Yep Flashcards
How many neurons are there in each tarsal sensilium?
Each trichoid sensilia in the tarsi house up to five taste neurons. The cell bodies of these neurons project dendrites toward the pore through which the tastants enter.
How many GR does Aedes have?
107
How much (in %) of CO2 is sufficient to activate mosquitoes?
roughly 4% exhaled in breath is a potent behavioral activator.
What does CO2 administration alone evokes?
Activates mosquito flight, increasing the probability of flight take-off and locomotor activity.
What do CO2 filament plume elicit?
Plumes elicit stereotyped and sustained patterns of upwind flight toward the CO2 source.
How is CO2 detected by OSNs?
By large-spiking amplitude OSNs housed within capitate sensilia in the maxillary palp.
Do mosquitoes always land on heated targets?
No, only when presented with a pulse of CO2 and homozygous Gr3 mutants did not land on a heated pad.
Are mosquitoes always attracted to Lactic acid?
No, lactic acid is not attractive on its own but only when CO2 is co-presented with it. Gr3 mutants did not respond to lactic acid.
Are mosquitoes attracted to nylon sleeves in the absence of CO2?
Only moderate, CO2 enhanced levels of attraction in females toward the nylon sleeve.
How do CO2, odor and heat synergize to drive blood-feeding?
They synergize in all binary combinations.
Do Aedes agypti feed on cold blooded animals?
Ae. aegypti have been observed to blood-feed on cold-
blooded animals such as lizards when warm-blooded verte-
brates were unavailable
Over what distance do mosquitoes perceive heat?
it is generally assumed that thermal convection
currents emanating from human skin rapidly dissipate to
reach equilibrium with ambient temperature conditions within
%1.5 m of the host
Are odors of human blend attractive by themselves?
Of the odorants that have been test, a small number, such as lactic acid, ammonia, carboxylic acids, 1-octen-3-ol, and nonanal increase mosquito attraction when presented together with CO2 but these are poor attractans by themselves. But mosquitoes are attracted to whole skin odor even in the absence of CO2.
What is Butyryl chloride?
Is a reactive volatile compound related to two of the strongest known inhibitors of the CO2 receptor, butyraldehyde and butyric acid.
What effect does butyrl chloride has?
A single puff of
1% butyryl chloride inhibits cpA from firing in response to sub-
sequent CO 2 stimuli
How is the response of cpA to binary mixtures of the two types of activators?
We find
that cpA’s response to a mixture of CO2 and skin odorant is additive, the response to the combined stimulus being significantly greater than its response to either stimulus alone.
This contrasts with Or-expressing neurons, where mixtures of
two activating odorants do not elicit stronger responses than the
stronger activator by itself.
Dios prior exposure to CO2 or skin odorant change the neural responses to following stimuli in cPA?
No
What does chemical inhibition of the cPA neuron do?
Reduces attraction by masking
detection of skin odor.
What does the presence of oscillators in all eukaryotic cell enambles organisms to do?
1) Make daily time-keeping possible, enabling animals to anticipate conditions rather than follow them
2) Enables animals to measure changes in the duration of daylight to detect changing of seasons (photoperiodism)
Do you think the circadiam rhytm might affect host seeking behavior?
- Examples of canopy (different species biting at different time in the forest canopy)
-Niche diversification
-Dennis: Zeitgeber time (ZT) 6-ZT10 at 25-28C and 70%–80% relative humidity
How does temperature affect gonotrophic cycles?
It determines the rates at which blood meal is digested and the ovaries develop.
What do all sensilia have in common in terms of structure?
1) One or more sensory neurons
2) two or three auxiliary cells
3) one or more glial cells
4) cuticular structures.
Describe contact chemosensilia (gustatory?)
The hair or peg is perforated by a single, large, apical pore, such sensialia are termed uniporous.
Describe olfactory sensilia?
The peg is perforated by numerous pores or slits, the sites of entry of odorant molecules.
Where are the cell body of sensory neurons situated?
They are situated immediately or a short distance below the integument.
How many neurons are there in chemosensory sensilia?
Between two and five and in gustatory one of these may be mechanosensory.
What is the function of odorant binding proteins?
Protect the odorants from degrading enzymes present in the lymph and, by diffusion, transport these across the sensilar sinus.
Is it possible that odorant binding protein play a role in odorant binding recognition?
It is possible but it is generally thought that the recognition is done by the receptors on the dendrite membrane.
Given an example that show that central sensory integration of chemosensory stimuli occur in mosquitoes:
Water-satiated Culiseta inornata which would not give labellar response when the arboral sensilla were touched with water, would do so if, at the same time, the tarsi were in contact with sucrose, revealing central integration of gustatory stimuli.
What are cooling cells?
Neurons with dendrites in the distal antennal segment (flagellomere 13) that are phasic thermoreceptors that respond to temperature change rather than absolute temperature and they express IR21a (Anopheles gambiae)
How long will the puff of CO2 be?
Greppi uses 4% CO2 for 20 seconds
Does loss of IR21a disrupt host-seeking?
It does not disrupt orientation toward sensory cues and argue against the presence of global deficits in the mutants
Describe the paper by Rogan and Rossignlo 1999
They modified a previously used olfactometer. When DEET was presented alone the mosquitoes moved toward the source. When combined lactic acid with DEET they did not observe any attraction or repulsion
What is the pH of DEET?
DEET is a neutral compound.
What is the evidence that DEET act directly on the mosquito and not in the vapour phase?
Rogan and Rossignol presented deet and lactic acid impregnated gauze pads side by side in a Petri dish, we observed the same inhibitory response. The deet–lactic acid trials gave significantly different results than the control. deet and lactic acid impregnated gauze attracted only 14% of the mosquitoes; using ethanol (the diluent for most repellents) as the control attracted 52% of the mosquitoes. They concluded that deet acts on the mosquito and not directly on lactic acid.
Furthermore, in Pellegrino et al.:
In response to the suggestion that DEET and odours may interact in the vapour phase, we first quantified the respective amounts of vapour-phase 1-octen-3-ol emitted from the stimulus pipette in the presence and absence of DEET, using solid-phase microextraction (SPME) followed by gas chromatography mass spectroscopy analysis (GC–MS). The SPME measurements coupled to GC-MS showed that the addition of a second filter paper containing pure DEET in the stimulus pipette had no significant effect on the release of 1-octen-3-ol (10−2 dilution). Thus, we can rule out any fixative role of DEET under the conditions used here.
Bahbot (2011): One possible explanation for the inhibitory effects observed for
DEET on responses of AaOR8 to octenol is that DEET might
reduce the amount of ligand available for delivery to the receptor.
This reduction in the amount of the proper ligand might be
accomplished by diminishing the amount of octenol present in the
solution due to the reactivity of the amide and carbonyl moieties
present in the DEET molecule with octenol. Extracts of
physiological solutions containing DMSO and octenol with or
without DEET revealed nearly identical quantities of both
compounds (Fig. 4).
Is the chemical structure of DEET similar to that of picaridin?
No, the chemical structure of DEET (N,N-Diethyl-meta-toluamide) is different from that of picaridin (known as Icaridin outside the US), which is also known as 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester.
DEET contains a toluene group and a diethyl group, while picaridin has a piperidine ring and a carboxylic acid ester. Although both chemicals are used as insect repellents, they have different chemical properties and mechanisms of action.
What was the effect of DEET on four OSNs stimulated with ten structurally diverse odours?
It was complex and dependent on odorant receptor, odour and concentration. In some OSNs DEET suppressed odor-mediated inhibition, in other it decreased activation.
Are DEET effect on OR response concentration dependent?
the effects of DEET were strongly concentration dependent, such that high odour concentrations often overcame the effects of DEET
Did DEET alone evoked a response of OR?
DEET presented alone, without odour stimuli, elicited no response above that evoked by solvent in ab2A and ab3A neurons, slightly activated ab2B neurons and slightly inhibited ab3B neurons; but responses were considerably smaller than those elicited by cognate odour ligands.
What are evidence that DEET scrambles the response at the level of the sensilim (two OSN)?
Notably, 1-octen-3-ol presented in a dilution of 10−2 had opposite effects on the two neurons housed in ab2 sensilla, inhibiting the ab2A neuron expressing OR59B–ORCO (Fig. 1d) and activating the ab2B neuron expressing OR85A–ORCO (Fig. 1e). Co-application of DEET inverted OSN responses to odour, leading to activation of the ab2A neuron (Fig. 1d) and suppressing the odour-induced activation of the ab2B neuron (Fig. 1e). Similar opposite effects of DEET were observed when the ab2 sensillum was stimulated with a different odour, 1-octanol
Pellegrino paper (2013) discuss:
- Scrambling hypotheses
- A single, naturally occurring polymorphism in an odour-specific odorant receptor can modify receptor interactions with an inhibitory odour and render the receptor insensitive to modulation by DEET.
What is the main take home message from Bohbot (2011)?
The data demonstrate that repellents can act as olfactory agonists or antagonists, thus modulating OR activity, bringing concordance to conflicting models.
What are all the functions attributed to DEET?
DEET may directly target insect
acetylcholinesterases, mosquito ORs and it may
chemically sequester a mosquito attractant.
How much DEET do typical formulations contain?
5 to 100%
How much picaridin do typical formulations contain?
5% to 20%
Can DEET act on ORCO?
Ditzen et al. (2008) previously characterized DEET interactions with Anopheles gambiae ORs co-expressed with AgOR7;
activation of AgOR2 by 2-methyl phenol and AgOR8 by racemic
1-octen-3-ol was differentially inhibited by DEET suggesting that
DEET selectively inhibited the different odor-specific subunits
(OR2 and OR8) rather than the common co-receptor (ORCO)
Can DEET evokes activity in OR when administered alone?
Yes, DEET administered alone activated AaOR2 in a concentration dependent manner.
What is the response of OR2 when DEET is administered with indole?
AaOR2 response to indole was only slightly
inhibited by DEET.
What is the response of OR2 when DEET is administered withoctenol?
AaOR8 response to octenol was
strongly and significantly inhibited by DEET. Ditzen: The B cell responded to 1-octen-3-ol with a
median effective concentration (EC50) of 1.7 ×
10−10
, which was shifted to 2.5 × 10−7 in the pres-
ence of DEET (Fig. 1D).
What was the effect of picaridin when administered with activating odorants to OR?
AaOR2 and AaOR8 were exposed to a range of IR3535 and
Picaridin concentrations (1027 M21022 M) in the presence of
their respective odorants indole and octenol (both at 1027 M)
(Fig. 5A and 5C). Both compounds strongly and significantly
reduced AaOR2 and AaOR8 responses to indole and octenol in a concentration dependent manner.
What is the dose of repellents required to induce effect at the electrophysiological leve?
Bahbot (2011): In our study, millimolar doses of repellents were necessary to
achieve both odorant-independent activation and odorant-depen-
dent inhibition of ORs. These high concentrations are consistent
with the high amounts of repellents required in commercial
formulations and the large quantities needed to elicit physiological
responses in mosquito OSNs [4,5,37]. While the amount of
repellents going into vapor phase is unknown, it is clear that large
quantities are required to achieve close range protection against
arthropod bites. At the physiological level, indole-sensitive neurons
were activated by DEET only at high concentrations (apparent
threshold of 100 mg).
Our observations have in common with prior studies that
DEET activates OSNs at extremely high concentrations consid-
ering the reported sensitivity of these neurons to their cognate
ligands. For example, in our study, both DEET and 2-U
respectively activate OR2 and OR8 at 1023 M while their
respective ligands are active at 1028 M
Does the common action of IR3535 and Picaridin suggest they target ORCO?
DEET and 2-U differentially inhibited odorant-
induced activity of AaOR8 and AaOR2, but in opposite
relationship with repellent induced activation, suggesting inde-
pendent OR binding sites for activation and inhibition. The
differential inhibitory activities of DEET and 2-U on AaOR2 and
AaOR8 suggest that inhibitory binding sites for these repellents
associate with the OR2 and OR8 subunits. Inhibitory activities of
DEET and 2-U may thus be more influenced by differences in
OR2 and OR8 sequence than the activities of IR3535 and
Picaridin.
DEET alone has been shown to inhibit several classes of OSNs. Explain:
DEET alone has been shown to inhibit several classes of OSNs
in insects, including lactic acid-sensitive OSNs in Ae. aegypti
[19,20], various Drosophila OSNs and the 1-octen-3-ol receptor
neuron of An. gambiae [4]. Ditzen et al. [4] showed that responses of
AgOR2 to 2-methylphenol and AgOR8 to racemic 1-octen-3-ol
were differentially inhibited by DEET in the oocyte system with
the strongest inhibitory effect on the latter
Is the interaction between receptor and DEET a labile on?
The inhibitory effects of all
four repellents were reversible upon fresh exposure to the odorant
alone, suggesting that the interaction between the inhibitors and
the ORs is as labile as the one between the receptor and its
cognate odorant.
What chemical structural similarity do DEET, IR3535 and picaridin share that might explain their broad action on evolutionary distant receptors?
DEET, IR3535 and Picaridin all possess an amide moiety.
Small amide derivatives have been shown to affect a wide range of
molecular pathways through allosteric regulation of various
proteins including proteases [39,40], the cannabinoid receptor 1
(CB1) [41], the a7 nicotinic acetylcholine [42] and GABA A
receptors [43]. The broad activity of such compounds is mirrored
by DEET’s inhibitory effects on phylogenetically unrelated cation
channels [4] and underscores that there might be alternative
modes of action yet unknown.
What is the effect of DEET on the OSNs that respond to lactic acid in the antenna?
It inhibits them.
Does DEET show insecticidal properties
Yes
Could DEET inhibit the perception of CO2?
CO2-evoked responses of the cpA cell were unaffected by DEET, suggesting that olfactory transduction mediated by the CO2 receptor is not affected by the repellent.
Syed and Leal: We found no
difference in neuronal responses, including spike frequencies
and magnitude and kinetics of the receptor potential, when the
carbon dioxide-sensitive ORN in the sensilla on the maxillary
palps (10) were stimulated with CO 2 in the presence or absence
of DEET [
Is the effect of DEET odor specific?
Yes, in Ditzen (2008) To investigate whether DEET inhibition of
electrophysiological responses of ab5B translated
to an effect on behavior, we carried out trap as-
says with 3-methylthio-1-propanol. Flies showed
potent attraction to 3-methylthio-1-propanol (Fig.
3E, left), and this attraction was significantly de-
creased by DEET (Fig. 3E, right). Odor-evoked
activity in the Or47a- and Or83b-expressing ab5B
neuron thus contributes to attractive behavior that
can be inhibited by DEET and allows us to cor-
relate a selective electrophysiological effect of
DEET with a behavioral phenotype. Consistent
with the failure of DEET to inhibit methyl acetate
responses of ab2 (Fig. 3B, top), DEET did not
alter behavioral responses to methyl acetate in the
trap assay (Fig. 3F). We were unable to test the
behavioral relevance of ab5A inhibition by DEET
because flies were not attracted to geranyl acetate
in our trap assays.
Is DEET effect on odor-evoked currents due to a change in ion permeability?
Ditzen analyzed current-voltage relation curves during ligand stimulation in the presence and absene of DEET. The effect of DEET on OR-evoked current was symmetric at positive and negative potentials, and no change in reversal potential was observed. This suggests a reduction in permeabilityof the channels affected by DEET, but no change in ion selectivity.
What other nonselective cation channels structurally unrelated to OR does DEET inhibit?
mouse TRPM8 (mTRPM8), the het-
erotrimeric rat olfactory cyclic-nucleotide gated
(CNG) channel, and the Drosophila ether-a-go-
go potassium channel (Fig. 4L). This suggests
that DEET may interfere generally with the ionic
permeability of a subset of cation channels.
What have Syed and Leal found (2008)?
Mosquito smell and avoid DEET directly and a trichoid sensilium responds to DEET in a dose-dependent manner that also responded to terpenoids. They found no difference in response when they administered DEET with 1-octen-3-ol.
What are terpenoids?
Terpenoids, also known as terpenes, are a large and diverse group of naturally occurring organic compounds that are found in plants, fungi, and some animals. They are derived from five-carbon isoprene units, which can be combined in a variety of ways to form a vast array of different terpenoids.
Terpenoids are responsible for many of the distinctive aromas and flavors of plants, such as the fresh, citrusy scent of lemons and the spicy aroma of cloves. They also have a wide range of biological functions, including acting as signaling molecules, serving as structural components of cell membranes, and providing defense against herbivores and pathogens.
Has DEET been shown to induce behavioral avoidance on its own?
This is controversial. Syed and Leal observed that DEET alone is sufficient to induce repulsion. Some indoor and field experiments cited in that paper also indicated that DEET acted as a repellent even when just CO2 was provided.
How many types of sensilia do max palp have?
They have only one morpholical and physiological type of olfactory sensilia, the peg sensilia on the fourth segment.
Does DEET evoke responses in the maxilarry palps?
Syed and Leal using quinquefasciatus have observed no responses to DEET in the >100 peg sensilla.
What was the DEET responsive ORN in Syed and Leal also responsive to?
It responded in a dose-dependent manner to terpenoid compounds such as thujone, ecualyptol and linalool (all reported as repellents)
Could it be that DEET might surppress the release of physiologically relevant compounds?
Syed and Leal observed a significant decrease in the amounts of the major compounds release from the skin, namely 6-methyl-5-heptn-2-one, octanal, nonanal, decanal, and gernayl acetone
Do males also avoid DEET?
Yes (Syed and Leal)
What organs are utilized once the mosquito makes contact with the host?
Labella and tarsi
What does the tick olfactory system consists of?
A pair of front tarsi that contain the Haller’s organ, and a pair of pedipalps. The receptor proteins in these two structures differ from the mosquito sensory receptors found in the antennae and max palps.
What receptors do tick express?
Chelicerata and Hexapoda are two subphyla of Arthropoda (ticks
belonging to Chelicerata and mosquitoes to Hexapoda). The ancestors of Chelicerata and Hexapoda diverged
about 300 million years ago from a common ancestor. An important difference between these two subphyla
is that Hexapoda have odorant, gustatory, and ionotropic receptors, whereas Chelicerata only have gustatory and
ionotropic receptors
For how long can DEET provide protection?
Some hours. Luker_Hansen (2023) reports up to 6 hours for both ticks and mosquitoes.
What class of organic compoounds does ar-turmenone belongs to?
Ar-turmerone belongs to the class of organic compounds known as sesquiterpenoids. Sesquiterpenoids are a type of terpenoid, which are organic compounds produced by plants and other organisms, and they are built from three isoprene units (15 carbon atoms in total). Ar-turmerone is a specific type of sesquiterpenoid that is found in the essential oil of turmeric (Curcuma longa). It is known for its potential health benefits, including anti-inflammatory and antioxidant effects.
In Luker and Hansen what three terpenes were common to all three best-performing oils (geraniol, cinnamon oil and clove oil?
Caryophhyllene (E-), Longifolene, and Myrtanol Acetate
What is the current standard testing method for contact repellency?
For mosquito contact repellency testing, the US EPA reccomends testing pesticide products through field testing or arm in cage assay both of which requires a live volunteer.
Is the terpene composition of essential oils?
It is very complex with individual oil containing dozens of different terpenes. Essential oils that contain few terpenes such as castor oil don’t repel mosquitoes or ticks (Luker_Hansen).
Is the solvent used going to affect the result?
Luker founds that the solvent used for essential oil repellent product greatly determines an essential oil’s property to repel mosquitoes and protect from bites.
What are the three mostly expressed OR in the yellow fever mosquito antennae?
AaegOR84, AaegOR113, and AaegOR11 are three of the most74
expressed ORs in the female yellow fever mosquito antennae
What does OR11 in Aedes responds to?
To many compounds including fenchone a potent repellent but did not evoke repellency compared to DEET in Wu and Leal (2022). It also responded to 2,3-dimethylphenol that has strong repellency activity.
What does the majority of glomerular projections target in Drosophila?
They target the lateral horn (Fisek, Wilson).
What did Fisek and Wilson shown in the lateral horn?
Here we show that lateral horn neurons (LHNs) receive input from sparse and stereotyped combinations of glomeruli that are
coactivated by odors, and certain combinations of glomeruli are over-represented. One morphological LHN type is broadly tuned
and sums input from multiple glomeruli. hese neurons have a broader dynamic range than their individual glomerular inputs do.
By contrast, a second morphological type is narrowly tuned and receives prominent odor-selective inhibition through both direct
and indirect pathways. We show that this wiring scheme confers increased selectivity. The biased stereotyped connectivity of the
lateral horn contrasts with the probabilistic wiring of the mushroom body, reflecting the distinct roles of these regions in innate as
compared to learned behaviors.
What is the lateral horn sufficient to do in terms of behavior?
it is sufficient to mediate behav-
ioral responses to odors that do not involve learned associations3,7,8,
and it receives the majority of glomerular projections.
What is a third option (apart from labelled line and combinatorial coding) to encoding of odors in higher order centers?
A theoretical study by Riffell proposed that LHNs might add and subtract sparse, weighted inputs from coactivated glomeruli. Suggesting that combinations of glomeruli should be overreprestented, namely glomeruli whose sum or difference represents a behaviorally useful computation.
What are the two classes of neurons in the lateral horn?
Fisek and Wilson identify two classes (Type I and Type II, dorsomedial and ventrolateral respectively) and they innervate different parts of the protocerebrum. The former are broadly tuned, whereas the latter were more selective. Type I neurons received inputs from 3 to 4 invariant glomeruli co-activated by many fruity-smelling organic acetates.
In Type I lateral horn neurons how was the postsynaptic responses when two inputs were activate together?
The postsynaptic response was accurately predicted by summing the responses to each input alone. So the input sum in a fairly linear manner, although they elicit modestly supralinear postsynaptic responses at weak presynaptic firing rates. Summing input in this manner could allow LHNs to be sensitive to a broader range of stimuli than any single one of their input glomeruli (they encode a broader range of concentrations as compared to their individual presynaptic PNs).
Describe the input of Type II lateral horn neurons:
It is narrower than the input to Type I neurons. In some cases just one PN from one glomerulus project to a type I neuron. This input might be gated by inhibition of other glomeruli which makes the LH not sensitive to all the odors of the cognate glomerulus.
What are the two sources of inhbition that gate activity and sensitivity in laterla horn neurons?
Some inhibition arises from a direct GABAergic projec-
tion from the antennal lobe, and additional inhibition arises from a
local GABAergic circuit within the lateral horn. Although inhibition
is much more prominent in type II neurons, it can occasionally be
seen in type I neurons as well
What is the relationship between glomerula inputs and synaptic weights?
In Drosophila (Fisek and Wilson): Our paired recordings also showed that different glomerular inputs
to an LHN can be associated with nonuniform and stereotyped syn-
aptic weights. This idea has been proposed previously as a way to
render LHNs more selective for a particular olfactory feature4. This
result also indicates a high level of precision in the development of
this circuit.
What could be the adaptive role of broadly tuned LH neurons?
Broad odor tuning to a group of related chemicals might
be a useful way to link a large region of chemical space (for exam-
ple, odors associated with fruit) with an innate behavioral program
(for example, feeding).
What do receptive fields represent in higher-order olfactory neurons?
In Drosophila, higher-order olfac-
tory receptive fields represent weighted sums of molecular features.
In other sensory systems, receptive field structures are nonrandom
insofar as they have a strong tendency to sample from overlapping
regions of stimulus space, reflecting the statistical regularities of the
environment
Wei_Dechering abstract
Here, we describe a
machine-learning-driven high-throughput method for the discovery of novel repellent molecules. To
achieve this, we digitized a large, historic dataset containing ~19,000 mosquito repellency
measurements. We then trained a graph neural network (GNN) to map molecular structure and
repellency. We applied this model to select 317 candidate molecules to test in parallelizable behavioral
assays, quantifying repellency in multiple pest species and in follow-up trials with human volunteers.
The GNN approach outpeormed a chemoinformatic model and produced a hit rate that increased
with training data size, suggesting that both model innovation and novel data collection were integral
to predictive accuracy. We identied >10 molecules with repellency similar to or greater than the most
widely used repellents.
Is picaridin effective against all mosquitoes?
No, (Wei, 2023), picaridin is effective against Aedes aegypti but is ineffective against Anopheles mosquito and is not reccomended for use in malaria-endemic regions.
What are the techniques used for discovery of new repellents and what repellents have each of these discovered?
Structure-targeted modeling of ORCO led to discovery of picaridin and VUAA1.
Scaffold hopping in combination with arm-in-cage testing, led to the discovery of IR3535 and DEPA
How diverse were molecules identified by ML in Wu (2023) compared to the USDA dataset?
we found that molecules selected by our
model are enriched in benzenoids, ethers, carboxylic acid derivatives, and organoheterocyclic
molecules when compared to the molecules measured by the USDA dataset
How many ORN does each sensilia house?
Typically two, but some house three or four ORNs.
How many OR does Drosophila express in the antennae and maxillary palps?
roughly 50
What is the ligand-ORN relationship that has been found in Drosophila?
Most individual ORN types respond to
multiple ligands, and most individual li-
gands activate multiple ORN types. The
best ligands for a neuron often do not fall
into a single chemical class.
What happens to the ORN firing rate when the ligand concentration increases?
The firing rate rise with increasing concentration; they have typical dynamic range of approximately two orders of magnitude in odor concentration. Increasing concentration tends to recruit responses in a larger number of ORN types and ORNs become broadly tuned at higher concentrations.
Are ORN responses dynamic?
Yes, spike rates peak rapidly and subsequently relax to a tonic level of activity.
What happens when you swap OR between ORNs?
Importantly,
swapping receptors between ORNs swaps their
odor responses (Hallem et al. 2004). Recep-
tor swap also recapitulates the dynamics of
odor responses. Thus, all of the diversity in
ORN odor responses is likely due to diversity
in ORN odorant receptor expression. In other
words, the different ORN types are function-
ally generic, except that they express different
receptors
What do some of the most selective ORNs respond to?
They respond to social odors. For example, two types of ORNs respond to CVA (cys-vaccenyl acetate) which is produced exclusively by males. These odors trigger robust behaviors. Some of the central neurons postsynaptic to these ORNs have unusual properties or patterns of connectivity, suggesting specialization for social odor processing.
Do ORNs fire spontaneously?
Yes, all ORNs fire spontaneously and each ORN type has a characteristic spontaneous firing rate. Mutating odorant receptor diminishes the spontaneous rate. In some cases an odor can inhibit spontaneous firing.
Are odors that are inhibitory per se?
No, most odors inhibit at least one ORN type while exciting other types, meaning no odors is inhibitory per see.
Kreher and Carlson: At the higher doses, most odorants inhibited at least one receptor, and most receptors were inhibited by at least one odorant.
Why could spontanoues activity be useful?
Spontaneous activity in ORNs is puzzling
from a functional standpoint because it sim-
ply adds noise to the system. Why hasn’t the
fly evolved odorant receptors that are inac-
tive when unbound? Spontaneous transduction
might be useful because it depolarizes the cell’s
resting potential to near its spike threshold. Al-
ternatively, it might just be difficult to evolve
a receptor protein with the requisite specificity
and kinetics that is never activated in the ab-
sence of a ligand
Describe how noisy ORNs are in Drosophila:
On average, a Drosophila
ORN fires 8 spikes/s in the absence of an odor
(de Bruyne et al. 1999, 2001). Because each
antenna contains 1,200 ORNs (Stocker et al.
1990), the brain is continuously barraged by
∼20,000 ORN spikes/s, even when no odor is
present.
How are most odors encoded?
By multiple ORN types with overlapping receptive fields.The recruitment of
multiple ORN types is also important because
each type is sensitive to concentration over a
restricted concentration range.
What are the three things that ORN responses depend on?
Every ORN odor response
depends on (a) odor identity, (b) odor con-
centration, and (c) the rate of change in odor
concentration.
Nevertheless, behavioral experiments indicate that
odor identity and concentration are encoded
independently in the Drosophila brain.
Do ORNs have correlated odor selectivity?
A
stimulus that evokes a high firing rate in a given
ORN type also tends to evoke a high firing rate
in many other ORN types. Conversely, a stimu-
lus that elicits unusually weak activity in a given
ORN type also tends to evoke weak or little
activity in most other ORNs. In other words,
there is substantial redundancy in ORN odor
representations (Haddad et al. 2010, Luo et al.
2010, Olsen et al. 2010). This too has important
implications for downstream odor processing.
What are the differences across glomeruli in flies?
The number of ORNs in a given glomerulus varies across glomeruli by a factor of about four and is correlated with glomerular size.
What does each glomerulus contain?
Each glomerulus contains the dendrites of several PNs, termed sister PNs; these sister PNs have highly correlated patterns of activity
How do PNs responses differ from ORNs responses?
PN responses show less variability in trial-to-trial spike count than do the responses of their presynaptic ORNs to the same stimulus.
They are more broadly tuned to odors than their presynaptic ORNs.
The odor responses of a PN can be sup-
pressed by recruiting additional activity
in other glomeruli. For example, when
mixed with a second odor, an odor that
elicits no response in a given PN when
presented alone can inhibit that PN’s re-
sponse to the second odor
How is Drosophila able to lateralize odor stimuli if ORNs arborize bilaterally?
This is explained by a small
asymmetry in ORN neurotransmitter release
properties: The ORN releases ∼40% more
neurotransmitter per spike from its ipsilateral
axon branch than from its contralateral axon
branch. As a result, when an odor stimulus is
lateralized, the PNs that are ipsilateral to the
stimulus spike at slightly higher rates and with
a slightly shorter latency than do those that
are contralateral to the stimulus
What neurotransmitters do PNs release?
They are cholinergic.
What happens if you silence input to other glomeruli?
The net effect of lateral input to a PN is generally inhibitory. A PN odor response is typically disinhibited by silencing input to other glomeruli. Conversely, adding new odors to an odor mixture typically produces either sublinear summation or frank suppression.
Can a PN be inhibited by a stimulus that actually excites its ORN?
Yes, because of lateral inhibition. These effects can be blocked by a combination of GABAa and GABAb receptor antagonists.
In the antennal lobe where is the site of lateral inhibition?
It is generally presynaptic, at the ORN axon terminal. Robust lateral inhibition requires active neurotransmitter release from ORN axons. When ORNs are silent, most lateral inhibition disappears.
What happens to the overall level of inhibition when stimulus intensity increases?
The overall level of inhibition in the antennal lobe rises with increasing stimulus intensity. These results imply that
the spatial pattern of GABA release depends
on the stimulus, thereby suggesting a model
where specific subsets of glomeruli are linked
by inhibitory subnetworks and ORN input to a
glomerulus recruits LN input to a specific sub-
set of other glomeruli
What is sufficient to predict PN sensitivity?
The total ORN activity alone; that is, the identity of the active ORNs did not matter. Indeed, PN odor responses could be predicted with high accuracy on the basis of only two factors: the firing rate of the PNs cognate ORNs and the total firing rate of the entire ORN population. This finding susggests a model whereby inhibition is global, meaning all glomeruli inhibit each other.
What do LNs innervate?
Some LNs innervate a relatively subset of glomeruli and could therefore permit specific interactions between glomeruli. However, most individual LNs innervate most or all glomeruli. Therefore, some glomeruli might be
interconnected in specific subnetworks. These
subnetworks might be created by LNs with sparse
innervation patterns or by electrical
compartmentalization within the arbors of broadly
innervating LNs.
Why would it be useful to segregate each ORN type into a different glomerulus?
Recall
that even when no odor is present, ORNs as a
population continuously barrage the brain with
∼20,000 ORN spikes/s. If ORNs wired ran-
domly to PNs, then the task of detecting (for
example) 10 odor-evoked spikes in this bar-
rage would seem hopeless. But, if all 10 spikes
were fired nearly synchronously by ORNs that
were presynaptic to the same glomerulus, then
they would likely summate effectively enough
to drive a PN above its spike threshold. Thus,
the orderly wiring of the olfactory system repre-
sents a computational machine par excellence:
an extreme and illustrative example of what has
been proposed to be a generally useful strat-
egy for organizing neural connectivity (Abbott
2008).
Why are PNs most sensitive to low ORN firing rates?
When sister ORNs are firing at a low
rate, small increases in their firing rate cause
relatively large increases in the firing rates of
their postsynaptic PNs (Olsen et al. 2010).
When ORNs are firing at high rates, they tend
to saturate their postsynaptic PNs. Conse-
quently, odor stimuli that elicit low ORN firing
rates occupy the lion’s share of a PN’s dy-
namic range (Bhandawat et al. 2007). Because
most odor-evoked ORN firing rates are low
(<50 spikes/s) compared with the maximum
ORN firing rate (∼300 spikes/s) (Hallem &
Carlson 2006), most of a PN’s dynamic range
may be devoted to the most common odor
stimuli (Figure 2). Thus, this property of PN
tuning should maximize rates of information
transmission (termed histogram equalization;
Laughlin 1981). In simulations, the compres-
sive nonlinearity in the relationship between
ORN and PN firing rates substantially im-
proves odor discrimination by a linear encoder
(Luo et al. 2010, Olsen et al. 2010)
How does lateral inhibition adjust PN sensitivity to the level of total ORN activity?
LNs collec-
tively pool input from all glomeruli, and they
inhibit ORN neurotransmitter release as ORN
activity increases. This behavior makes PNs
less sensitive to the firing rates of their cognate
ORNs (Olsen et al. 2010, Olsen & Wilson
2008, Root et al. 2008). As a consequence of
inhibition, PN firing rates do not saturate as
easily as they would otherwise, and their dy-
namic range becomes more closely matched to
that of their inputs (Figure 2). In simulations,
this type of lateral inhibition substantially im-
proves odor discrimination by a linear decoder.
In particular, it improves a decoder’s ability to
identify an odor in a concentration-invariant
manner (Luo et al. 2010, Olsen et al. 2010),
implying that lateral inhibition may help flies
identify odors in spite of natural variations
in odor concentration. Lateral inhibition also
decorrelates the activity of different PNs. The computation
implemented by this type of lateral inhibition
has been called divisive normalization, and
it appears to play a role in a wide variety of
sensory systems
How do glomeruli differ from one another molecularly?
Glomeruli differ in their
levels of neuropeptide and neurotransmitter
receptor expression; they may also differ in sen-
sitivity to neurotransmitters (Nassel et al. 2008;
Root et al. 2008, 2011).
What behavior do odors that activate multiple glomeruli evoke?
Odors that activate multiple glomeruli elicit a
behavior that can be accounted for by summing
the weights associated with each glomerulus
(Semmelhack & Wang 2009). This summation
would predict that coactivating two attractive
glomeruli would always produce attraction,
never aversion. Is this true? Notably, many
odors are attractive at low concentrations but
aversive at higher concentration
Why are some odors attractive at low but aversive at high concentrations?
This observa-
tion can be reconciled with the sum-of-weights
model, but only if the receptors for aversive
glomeruli are systematically recruited only
at high odor concentrations, implying low
ligand-receptor affinities.
What are the four steps that Duncan used to analyze individual swim bouts to determine their stereotypy.
1) Reduced dimensionality of the tracked data.
2) Computed the distance between each pair ofbouts.
3) Combined similar bouts into exemplars by micro-clustering
4) Non-linear embedding using the distances between exemplars to generate the final behavioral space.
How does non-linear emedding differ from linear embedding?
The goal of non-linear embedding is to find a mapping that can transform the original data into a lower-dimensional space, while preserving the local and global relationships between the data points. Unlike linear embeddings, which use linear transformations such as principal component analysis (PCA), non-linear embeddings use non-linear transformations that can capture more complex relationships between the data.
One popular non-linear embedding technique is t-SNE (t-distributed stochastic neighbor embedding), which maps high-dimensional data points to a two- or three-dimensional space, while preserving the local structure of the data. Another example is UMAP (Uniform Manifold Approximation and Projection), which is a newer algorithm that uses a different mathematical framework to achieve similar results as t-SNE.
Why are movements believed to lie on a low-dimensional manifolds?
Mechanical and neural constraints impose limits on the
possible posture configurations for an animal;
How did Duncan reduced the dimensionality of data?
As our tracking provides overly redun-
dant measurements along the tail, we performed principal
component analysis (PCA) on the sequence of all tail postures.
Three PCs explained 85% of the variance in tail shape (Fig-
ure 1D). These PCs define postural modes and can be repre-
sented by a set of tail shapes known as ‘‘eigenfish’’ [17, 34, 35]
(Figure 1E). As posture is dynamic over time, these shapes trace
a trajectory in three-dimensional coordinate space
How did Duncan measured distance between different bouts of temporally varying postures?
He used dynamic time wapring, which handles temporal offsets and small variations better than Euclidean distance. From these dis-
tances, we generated micro-clusters (each represented by a single exemplar) using affinity propagation
What does isomap embedding allow for?
Next, we performed isomap embedding [39] using the DTW
distances between exemplars (Figure 1I), which preserves
global behavior structure preferentially to local structure. We
could not discern any additional structure if we embedded all
bouts, suggesting that we were not losing information about
the structure of behavior by only embedding exemplars
How did Duncan investigate the temporal organization of bout sequences for structure and stereotypy?
He decomposed the one-step transition frequency matrix between micro-clusters into a set of transition modes, each of which captures some feature of temporal behavioral dynamics.
How did Dunca assessed whcih of the transitions were signficiant?
He compared the observed probabilites to randomly shuffled bout sequences.
How do ORNs respond to increased concentration of an odor (Carlsson, Hansenn)?
With an increase in action potential frequency.
Is the most active glomerulus the same across concentrations or does it differ?
Carlsson and Hansson noticed that in the moth Spodopter littoraliis the most active glomerulus was concentration-dependent. Activity foci were only persistent across concentrations in 25% of the recorded concentration series. However, movement of activity focus was generally restricted to adjacent or proximal glomeruli.
What happens to the number of activated glomeruli with increased concentrations?
The number of activate glomeruli increases. Dose response-curves often reach a plateau in the most strongly responding glomeruli, suggesting a sigmoid function.
Describe correlation of responses of glomeruli exposed to odors?
Similarity is highest between responses evoked by the same compound. The correlation, however, decreased when the difference in concentration between stimuli increased. In some instances the glomerular patterns were actually more similar across odorants than across concentrations. The pattern evoked by distinct compounds tend to be more similar to each other when each is at highest concentration. However, this effect seems to depend on the similarity of the odorants.
How do ORNs differ to PN and LN in responsivness to concentration?
In
contrast to ORNs, LNs and PNs are often much less
concentration-dependent and many interneurons do not
express increased spike activity at concentrations above
threshold levels.
What does GCaMP cosnsits of?
A circularly permuted EGFP flanked on one side by the M13 fragment of myosin light chain kinase and on the other by the calcium binding site of calmodulin. In the presence of calcium, calmodulin interacts with the M13 fragment eliciting a conformational change in EGP resulting in elevations in fluorescent intensity that reflect changes in the intracellularcalcium concentration.
What enhancer trap line did they use to restrict expression of GCaMP to projection neurons in Wang?
An enhancer trap
line, GH146-Gal4, has been characterized that drives
the expression of Gal4 in approximately 90 of the 200
PNs (Stocker et al., 1997; Jefferis et al., 2001). This subset of PNs innervates 34 of the 43 antennal lobe glomeruli (Laissue et al., 1999).
Explain the method used by Wang for the antenna-brain preparation.
1) Fly was decapitated
2) Cuticle and connective tissue were removed from the head by microdissection to reveal the brain and attached antennae.
3) Specimen is embedded in agarose gel, and the antennae were exposedto allow quantitative delivery of odors via an olfactometer. This preparation provided responses up to five hours.
How was the glomerular response at low concentrations in Wang (2003)?
At low odor concentrations, the glomerular response
is sparse. Exposure to three different odors, 1-octen-3-
ol, hexane, and isoamyl acetate at 8% saturated vapor
concentration (SV), reveals that each odor elicits a different pattern of glomerular activity and these patterns are
conserved among different animals (Figure 1). At 2%
SV, many odors fail to elicit a significant response and
those that do activate a small number of glomeruli. At higher odor concentrations, the number
of glomeruli activated by a given odor increases to reveal
a dense map with individual odors activating from two
to as many as 15 of the 23 glomeruli analyzed (Figures
2 and 3). The response to six odors at 33% SV results
in a denser map with greater overlap. The VM2 and DM2
glomeruli for example respond to four or five of the six
odors tested
Talk about the variability in the glomeruli of the antennal lobe:
The variability in antennal lobe structure appears at first to contrast with Drosophila melanogaster, where each glomerulus can be
clearly identified and named. However, we note that the antennal lobe map in Drosophila melanogaster has been refined with the advent of new genetic techniques, starting with 35 glomeruli in the original atlas (Stocker et al., 1990), then modified to 40 glomeruli
(Laissue et al., 1999), and further refined in numerous studies
(Couto et al., 2005; Fishilevich and Vosshall, 2005; Tanaka et al.,
2012) including a recent count of 54 (Grabe et al., 2015) and 58
(Task et al., 2020) glomeruli. We have refrained from naming glomeruli in Ae. aegypti at this time because we believe that a more stereotyped anatomy will emerge as new genetic lines are generated that allow cell-type-specific labelling.
What other advtanges does high resolution tracking of flying trajectories have?
mproving the resolution, and increasing the
dimensionality, of the common low dimensional and end point behavioral assay has the potential to increase the predictive
validity of translational repellent and to increase the rate at which basic science findings are
translated to the field.
Could the trajectory be more indicative of repellency than the time spent in contact or number of landings event?
It might, in Abdoo-Saboor: Additionally, these data demonstrate that the nature of the
response when an animal withdrawals its paw might be a more reliable indicator of pain state than
the number of times the animal lifts its paws to a given stimulus. In other words, paw withdrawal fre-
quencies revealed great variation across the seven strains (Figure 1), whereas paw trajectory pat-
terns to a given stimulus showed quite stereotyped responses among these strains (Figure 2).
How did they calculate an univariate pain score in Saboor?
The seven behavioral features we extracted from video each provide more useful information than
paw withdrawal frequency alone. Nevertheless, the simplest way to score behavior is using a univari-
ate pain scale derived from these behavioral features. To accomplish this, we used ordinal logistic
regression to identify a univariate linear subspace of the seven behavioral features that best sepa-
rates the four somatosensory stimuli: CS, DB, LP, and HP. We did this for two cases: first, restricting
to just four features quantifiable in the pre-peak period (t < t*), and then for all seven features quan-
tified during the post-peak period (Figure 4H and I, respectively). For both the pre- and post-peak
paw features, the two no-pain stimuli (CS and DB) cover the same parts of the subspace and are
largely indistinguishable. By contrast, the low and high pain conditions (LP and HP) clearly separate
from the no-pain stimuli and also separate from each other in this univariate pain score.
How did they evaluate the univariate pain score?
The performance of the univariate pain score was evaluated by leave-one-out (LOO) cross-valida-
tion for individual mice (Figure 5A), and by leave-one-strain-out for strains (Figure 5B). We com-
pared the pre- and post-peak paw univariate pain scale classifications to a null model that assigns
pain classes according to their probability in the training data, without reference to measured behav-
ioral features. For prediction, CS and DB were treated as a single ‘no-pain’ class, while LP and HP
were treated as a single ‘pain’ class, resulting in a binary classification: no-pain or pain (Figure 5—
figure supplement 1).
What does the arm-in-cage and other endpoint assays lack?
hile this methodology for measuring pain in rodents is not fundamentally flawed, it lacks
resolution – a limitation that can now be overcome with advances in videography and automated
tracking. Here, by automatically tracking paw dynamics at sub-second speeds with high-speed vide-
ography coupled with machine learning approaches, we reveal stereotyped trajectory patterns in
response to innocuous versus noxious stimuli spanning genetically diverse mice. With an accurate
pinpoint of the paw at high spatiotemporal resolution, a freely available software package we term
PAWS automatically quantifies seven behavioral features that are combined to determine the mouse
pain state.
Is there evidence for resistance to DEET?
Lima-Camarra: he field (Laranjeiras, Sergipe, Brazil) and laboratory
(Rockefeller) populations were characterized for the presence of the Val1016Ile kdr mutation, associated with
pyrethroid resistance, and locomotor activity. Repellency bioassays were performed to assess the response
of the mosquitoes to human odor by exposing them to 10% DEET applied to the skin in ethanol. Samples
from the field population showed higher frequency of the kdr mutation, 21.9% homozygous and 21.9% het-
erozygous, greater locomotor activity and greater sensitivity to DEET than the laboratory population. These
results suggest increased sensitivity to DEET in field populations and a possible interaction between insecti-
cide exposure and sensitivity to DEET.
Is Dengue still endemic in Brazil?
Since the introduction of yellow fever (1685), dengue (1845),
chikungunya (2014), and Zika (2015) arboviruses, epidemics are re-
corded in different regions of Brazil (Zanotto et al. 2018). Urban
yellow fever is considered eliminated since 1942, but the recent virus
circulation through the Southeastern Region in the second half of
2017 have caused the biggest wild epidemic in the last 80 yr (Possas
et al. 2018). Despite dengue epidemics are increasing in time over
the last decades, the challenging neurological problems in newborns
associated with Zika virus and rheumatic sequelae of chikungunya
virus, national policies are still based on the same standard strategies
to Aedes aegypti (Linnaeus, 1762) control as house survey, use
of larvicidal products and ultra-low volume (UBV) nebulization.
List the evidence for resistance to insecticide in Brazil:
Due to these control policies, mosquito populations are under
high pressure of insecticides and a number of studies have shown
Ae. aegypti resistance to the groups of insecticides used to vector
control in Brazil, such as organophosphates (Macoris et al. 1999, La
Corte et al. 2018) and pyrethroids (Macoris et al. 1999, Luna et al.
2004, Linss et al. 2014, Liu 2015). In addition, the use of domestic
insecticides increases the resistance to these products, especially to
the pyrethroid (Gray et al. 2018). More recently, changes in the sus-
ceptibility of Ae. aegypti to the larvicide pyriproxyfen (currently in
use) have also been reported (Campos et al. 2020, Carvalho et al.
2020)
What are the main mechanisms of insecticide resistance?
The main mechanisms of insecticide resistance involve structural
changes in target sites, in the case of pyrethroids mutations in the
voltage-gated sodium channel gene, known as knockdown resistance
(KDR), and metabolic resistance due to the increased insecticide de-
toxification capacity mediated by enzymes such as esterases and
multi-function oxidases. These two mechanisms modify vector performance in terms of physiologic, reproductive and neural functions.
What are some of the consequences of Ae. aegypti pyrethroid resistance
Among reported
consequences of Ae. aegypti pyrethroid resistance are fitness change
(Brito et al. 2013, Viana-Medeiros et al. 2017) increased locomotor
activity (Brito et al. 2013, Nakazato et al. 2021) and decreased re-
sponse to spatial repellents (Wagman et al. 2015, Amelia-Yap et al.
2018). Voltage-gated sodium channels are reported to be implicated
in the electrical message from the olfactory receptor neuron to the
central nervous system (Zwiebel and Takken, 2004) so that KDR
mutations are likely to affect response to olfactory stimulus. In fact,
the pyrethroid resistant Ae. aegypti Puerto Rico strain was less re-
sponsive to several kinds of repellents than the susceptible Orlando
strain (Yang et al. 2020). Andreazza et al. (2021) confirmed cross-
resistance between KDR resistance and tolerance to transfluthrin in
Rockefeller (ROCK) strain, but failure to demonstrate tolerance to
N,N-diethylmethylbenzamide (DEET).
Would resistance to pyrethroids remain high in the population?
As resistance to pyrethroids has been
associated with a high fitness cost for Ae. aegypti (Brito et al. 2013),
a resistance-reversal trend would be expected some generations
after discontinuation of the selective pressure (Garcia et al., 2019).
However, as pyrethroid use remains high in domestic applications and commercial fumigation services (Clayton and Sander 2002, Diel
et al. 2003), resistance is expected to persist in field populations, as
observed in our study
Does KDR resistance affect DEET repellency?
No. Studies have shown that in populations resistant to pyrethroids,
organophosphates, and carbamates, the activity and number of
detoxifying enzymes of the P450 enzyme complex may be changed be-
cause of overexpression of the genes encoding these enzymes (Djouaka
et al. 2008, Bonnet et al. 2009, Liu 2015). Changes in monooxygenase
levels and overexpression of genes encoding these enzymes have been
found in resistant populations. Bonnet et al. (2009) demonstrated that
cytochrome P450 is responsible for the increased toxicity of DEET
and for the synergistic effect between DEET and propoxur. Although
the mechanisms behind this finding remain unclear, there is growing
evidence for the association between cytochrome P450 enzymes and
DEET activity (Corbel et al. 2009, Ramirez et al. 2012, Koloski et
al. 2019) as well as the synergistic effect between DEET and various
classes of insecticides (Bonnet et al. 2009, Pennetier et al. 2009, Faulde
and Nehring 2012, Abd-Ella et al. 2015).
Is there some insensitive strain you could validate it with?
There is a laboratory strain of Anopheles gambiae that was susceptible to insecticides but only weakly repelled by DEET, whereas other strains of this species that were resistant to pyretrhoids were repelled by DEET.
What is a semiochemical?
It is a natural volatile and non-volatile substance involve in the intra and or interspecific communication between organisms.
What type of sensilia house OSNs that express ORs?
Single-walled (basiconic or trichoid) sensilla. ORCs that respond to compounds such as ammonia, short
chain carboxylic acids and amines are housed in double-walled
(grooved peg and coeloconic) sensilla (Pappenberger et al., 1996;
Diehl et al., 2003; Benton et al., 2009; Hussain et al., 2016) and
do not express ORs but instead IRs. The IRs form ionic channels
activated by ligands (Benton et al., 2009) and are expressed
with one or two broadly expressed co-receptors different from
ORCO
How do sympatric moth release pheromones to attract conspecifics?
For instance, different strains of the
European corn borer (Ostrinia nubilalis) are attracted to precise
pheromone blend ratios (Klun et al., 1973). Similarly, different
species of Yponomeuta moths, which feed on the same host and
share the same three pheromone constituents, are reproductively
isolated due to differential attraction to species-specific blend
ratios (Löfstedt et al., 1991). Similar findings were also reported
on aphids (Dewhirst et al., 2010) and plant bugs (Byers et al.,
2013). While the importance of ratios is crucial for the design of
trap lures, the neural mechanisms underlying this phenomenon
just began to be understood
How is information about the female sex pheromone processed in moth and cockroaches?
In moths and cockroaches, information about the female sex
pheromone is processed by a small number of male-specific AL glomeruli forming a distinct structure, the macroglomerular
complex (MGC; e.g., Boeckh and Boeckh, 1979; Hildebrand
et al., 1980). Although the MGC sub-system of moths is
distinctive and particularly large, the synaptic organization and
structure of its constituent glomeruli is akin to that of the
rest of the AL glomeruli. In some moth species, each MGC
glomerulus processes a cognate pheromone component (e.g.,
Heliothis virescens; Berg et al., 1998), but in other species multiple
components are encoded in the same MGC subcompartment
Explain the manduca sexta odor induced orientation behaviors in male.
Because only these
two components (out of eight total) are required to elicit odor-
induced orientation behaviors in males (Tumlinson et al., 1989),
this provides a simple binary system to investigate the neural
mechanisms mediating pheromone processing, including blend
ratio processing. When males are stimulated with the pheromone
blend, two distinct populations of ORCs are specifically activated
by those two essential components, one evoking excitatory
responses in Cumulus projection neurons (cPNs) and the other in
Toroid projection neurons (tPNs; Kaissling et al., 1989; Hansson
et al., 1992; Hildebrand, 1996; Heinbockel et al., 1999; Lei et al.,
2002). Additionally, recent findings suggest that cPNs and tPNs
correlate their synaptic output to signal the presence of the
pheromone blend (Lei et al., 2013; Martin et al., 2013). In
principle, the odor-evoked spiking activity of cPNs and tPNs
could serve to report the chemical identity and concentration of
each blend component. However, since their outputs converge
in the same regions in the protocerebrum (the delta region of
the lateral horn and the mushroom body calyces), the relative
timing of input spikes from cPNs and tPNs in postsynaptic
neurons may have a physiological effect, that is, coincident spikes
would evoke a stronger response in postsynaptic neurons than
sequential spikes, allowing the representation of an odor mixture
as a single odor object (see also Section Effects of Background
Odor).
What is the evidence for synchrony in the antennal lobe?
Indeed, using simultaneous dual-electrode intracellular
recordings, Lei et al. (2002) showed inter- and intra-glomerular
spike synchrony among PNs in response to pheromone blend
stimulation. Odor-induced interglomerular synchrony in the
AL was also reported in cockroaches using voltage-sensitive-dye
imaging methods, suggesting that the synchrony code operates at
a broad spatial scale (Watanabe, 2012). Moreover, experiments
that simultaneously recorded neuronal activity across the
glomerular array in M. sexta showed that neurons with the most
similar odor response profiles produced the highest degree of
coincident spikes (Lei et al., 2004). These results support the
notion that PNs may use a correlative neural code. Further, it
has been shown that spike coincidence in M. sexta AL neurons
is modulated by the pheromone blend ratio. Behaviorally,
the moths respond best to the mixture of the two essential
pheromone components at the naturally occurring 1:2 ratio,
and deviations from this ratio deteriorate blend attractiveness
(Martin et al., 2013).
How is correlation of PN output in the antennal lobe obtained?
The mechanisms determining spike correlations are
unknown, but balanced inhibition may be involved. Upon
pheromonal stimulation, both PNs and LNs are activated, with
cPNs and tPNs excited by their cognate pheromone constituents
and reciprocally inhibited through GABAergic LNs (Lei et al.,
2002). LNs likely respond in a dose-dependent manner, allowing
the inhibitory effect exerted onto PNs to be modulated by the
relative proportion of the blend constituents. Moreover, the
degree of spike coincidence between PNs is positively correlated
with the strength of the inhibitory input onto those PNs (Lei
et al., 2002). Similarly, in the AL of cockroaches, GABAergic
LNs also mediate synchronization of PN outputs (Watanabe,
2012). Thus, balanced lateral inhibition is a plausible mechanism
by which stimulation with a pheromone blend of optimal ratio
can produce the highest degree of correlated spikes in PNs.
Do you think that CVA is encoded by a labelled line?
The odor-evoked spikes of PNs innervating a particular glomerulus DA1 are highly correlated and provide converging input to their target neurons in the lateral horn.
What, in addition to the identity of sex pheromone constituents is of paramount important for the behavior eliecited?
The constitutens ratios
Is there examples of aggregation pheromones in mosquitoes?
Yes, Culex quinquefasciatus gravid females, which
are vectors of filariasis and West Nile Virus (among others),
are attracted to a pheromone released from maturing eggs
in conjunction with an indole compound derived from grass
infusions (Mboera et al., 2000; Logan and Birkett, 2007),
and these components evoke electrophysiological activity from
antennal ORCs
What disease does Culex quinquefasciatus transmit?
Filariasis and West Nile Virus. Culex mosquitoes
are major vectors of pathogens including the human filarial
nematode, Wuchereria bancrofti, and arboviruses such as St. Louis
encephalitis, Japanese encephalitis, Venezuela equine encephalitis,
Western equine encephalitis and West Nile virus.
Can an alarm pheromone function as an aggregation pheromone?
Yes, depending on its concentration. This has been shown for trans-2-hexenal in cockroaches and in Rhodnis prolixus.
What are some manipulation of host-seeking behavior that show non-intuitve results?
1) Insects usually respond to specific mixtures of host odorants, even when they include ubiqutitous odorants.
2) Even when some cosntituents of those mixtures are essential to evoke a behavioral response, in some cases certain components could have redundant roles and therefore could be removed without decreasing attraction
3) Moreover, key components could be replaced without affecting attractiveness.
