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Optogenetics Flashcards

1
Q

define optogenetics:

A
  • use of light to regulate activity of neurons
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2
Q

optogenetics: how does it work?

A
  • cells genetically engineered to possess light responsive ion channels= control neuronal activity
  • these ion channels cloned from organisms responsive to light
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3
Q

optogenetics: eg. used (2) and ions

A

green algae: channelrhodopsins (+ve ions)

halobacteria: archaerhodopsins (proton pumps- remove +ve ions)

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4
Q

optogenetics: method to inject

A
  • virus carrying specific opsin (channelrhodopsin) and identifier for specific neuron type (promoter) injected into brain area to infect cells of interest
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5
Q

optogenetics: how to activate ion channels

A
  • using lasers

- alters activity of infected neurons

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6
Q

optogenetics: light wave/ freq and which commonly used?

A
  • electromagnetic radiation many freq, can only see small proportion
  • common colours used: blue, yellow, green
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7
Q

optogenetics: to activate use which light and action caused- channelrhodopsin (ChR2)

A
  • blue light
  • lets +ve ions into cell
  • cell stimulated
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8
Q

optogenetics: to activate use which light and action caused- halorhodopsin (NpHR)

A
  • orange/yellow light
  • lets Cl- ions in
  • cell inhibited
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9
Q

optogenetics: to activate use which light and action caused- achaerhodopsin (Arch)

A
  • orange/yellow light
  • pumps +ve ions out
  • inhibits cell
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10
Q

optogenetics: opsins tagged w wat? eg.

A
  • tagged w fluorescent protein so visualise infected neurons under microscope
  • ensures labelled correct cells w channels

eg. green fluorescent protein (GFR) or mCherry

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11
Q

optogenetics: how to check functioning of channel

A
  • electrophysiology
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12
Q

optogenetics: why use it?

A
  • electrical stimulation affects all neurons in area, incl fibres of passage
  • neuropharm: all neurons w that type of receptor in area drug is administered
  • optogenetics: specific to neuron/circuit u r targeting (others not affected)
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13
Q

optogenetics: process of using opsin to find circuitry

A
  • virus injected into B
  • opsin expressed through B (also fibres to A and C)
  • by laser activating B axons on A, corresponding B cell bodies r affected
  • by activating terminals at A only affecting neurons that come from B (where virus was injected)
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14
Q

optogenetics: process involving locus coeruleus (LC) and amygdala

A
  • virus w photosensitive channels in LC
  • while plant optrode (holds optic fibre in place) in amygdala
    = only neurons from LC to amygdala will be stimulated
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15
Q

optogenetics: bidirectional control of neurons process

A
  • mixed viral injection of opsins w diff lightwave spctrum into mixed pop of B (activator, inhibitor opsins)
  • opsin expression in B cell bodies to A and C
  • differentiate which opsin activated by using diff coloured lasers, due to photosensitivity of ion channels to diff wavelengths of light
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16
Q

optogenetics: use in humans and eg. (4)

A
  • possibly used
  • similar invasive procedure of deep brain stimulation, optic tech to target particular neuron type
  • schizophrenia
  • anxiety
  • depression
  • drug addiction
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17
Q

anxiety vs fear response features

A
  • universal human emotion, necessary to adapt to env
    fear: defensive behaviours, arousal, -ve emotions
    anxiety: reactions due to anticipation of -ve event
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18
Q

fear: subcortical and features- immediate response to a threat

A
  • subcortical
  • visual, auditory stimuli reach thalamus, travel to amygdala
  • amyg alerts other brain structures (hypothalamus- HPA axis and locus coeruleus: LC)
  • surge in cortisol and nAd = sweaty palms, tachycardia, increased BP

fight or flight response

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19
Q

fear: cortical and features- cognitive processing immediate response to a threat

A
  • cortical
  • info sent from thalamus - cortex and basal ganglia for cognitive processing
  • regions analyse raw data from sensory organs and decide dis/continue fear response
  • if maintained response: amyg remains on alert (helps make further appropriate behavioural responses)
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20
Q

amygdala: function

A
  • key area in processing fear, anxiety
  • esp basolateral (BLA) and central nuclei
  • alerted when emotional processing, or emotional response required
21
Q

amygdala: name subregions and sig

A
  • BLA: basolateral
  • CeM: central medial amyg believed to drive fear response
  • CeL: central lateral amyg
22
Q

no amygdala=

23
Q

amygdala: experiment to test how portions connected- activating BLA-CeL? results

A
  • blue light
  • reduced anxiety in elevated + maze
  • reduced anxiety in open field test (rat crossed through box vs. staying towards edges)
  • anxiolytic (reduce anxiety) effect = BLA activates CeL, reducing CeM output
24
Q

amygdala: experiment to test how portions connected- inhibiting BLA-CeL?

A
  • inhibiting w eNpHR3 (halorhodopsin)
  • 👷🏻
  • enhanced anxiety
25
amygdala: experiment to test how portions connected- activation of BLA result, summary
- activating BLA released glutamate in CeL to stimulate GABA cells and inhibit fear response of CeM - optogenetic activation of BLA terminals in CeL reduces anxiety stopping output of CeM
26
oxytocin: features (6)
- social neuropeptide - social interaction w peers - form monogamous pair bonding - sexual arousal, orgasm - maternal behaviour - social memory, anxiety reduction (anxyiolytic)
27
oxytocin: where in brain
- produced in magnocellular neurosecretory cells of hypothalamus - magnocellular cells in paraventricular nuclus (PVN) of hypothalamus (lateral/medial section) and supraoptic nucleus of hypothalamus (near optic tracts)
28
oxytocin: where to- from supraoptic nucleus
- volume transmission | - not so much neuron to neuron contact
29
oxytocin: where to- from paraventricular nucleus (PVN)
- classic neuron to neuron contact and vol transmission - oxytocin receptors in brain aka OT receptors neurons to: - nucleus accumbens (NAS) - bed nucleus stria terminalis - amyg (CeA, MeA) - dopamine cells of VTA
30
oxy release in central amyg reduce fear response? experiment features general
- link of opsin ChR2 to oxytocin promoter so only oxy cells targeted
31
oxy release in central amyg reduce fear response? result
- yes | - activating ChR2 on oxy terminals of CeL of amyg reduced fear in rats
32
list core brain regions receiving dopamine from VTA: (7)
- subthalamic nucleus - striatum - orbitofrontal cortex - prelimbic cortex - nucleus accumbens - amygdala - hippocampus
33
dopamine received from VTA function: striatum
habit
34
dopamine received from VTA function: orbitofrontal cortex
impulsivity
35
dopamine received from VTA function: prelimbic cortex
decision making
36
dopamine received from VTA function: nucleus accumbens
saliency/ motivation
37
dopamine received from VTA function: hippocampus
context/ memory of drug use
38
PFC-NAc connection: for dopamine
- prelimbic cortex (PL) of prefrontal cortex. (PFC) has glutamate (+ve) connections back to VTA dopamine cells and nucleus accumbens (NAc)
39
cocaine: method for rats
- intravenous drug self-administration (lever press)
40
cocaine: function at synapses
- DAT = dopamine transporter | - cocaine blocks DAT, modulation of DAT increases dopamine in synaptic cleft
41
reinstatement of cocaine seeking: list 3 tests done
- inject ArchT opsin/virus at PFC, laser via optrode on PFC - inject ArchT on NAc, and laser too - inject ArchT on PFC, laser on NAc
42
reinstatement of cocaine seeking: inhibition of PL (prelimbic) cortex-
- prevents drug seeking behaviour produced by re-exposure to cocaine
43
function of PFC neurons in rats displaying addiction phenotype: type of cell, features
- pyramidal neuron | - cocaine use resistant to inhibition by -ve consequence
44
function of PFC neurons in rats displaying addiction phenotype: hypoactive neurons result
- willing to keep taking cocaine despite shock (-ve consequence)
45
function of PFC neurons in rats displaying addiction phenotype: activation of PL cortex (somatic method) in shock resistant rats?
- reduced cocaine seeking in shock resistant rats
46
function of PFC neurons in rats displaying addiction phenotype: inhibition of PL cortex (somatic method) in shock sensitive rats?
- increases compulsive cocaine seeking in shock sensitive rats
47
summary: CeL function
- act as modulator of neuronal output of CeM | - CeL stops anxiety output of CeM
48
summary: oxy release in CeL causes
reduces fear responses
49
DREADDS: define
designer receptors exclusively activated by a designer drug | - targets specific brain cells if virus targets promoter

EXP NEURO (10 decks)

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