12 - Neurotransmitters Flashcards
3 fates of neurotransmitters after synaptic transmission?
- Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells
- Enzymes inactivate neurotransmitters
- Neurotransmitters can diffuse out of the synaptic cleft
6 criteria for neurotransmitter substance:
- Presence and synthesis
- Release
- Identity of action
- Pharmacology
- Inactivation
- Behavioural criteria
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- Release
- Identity of action
- Pharmacology
- Inactivation
- Behavioural criteria
-
Presence and synthesis
- The presynaptic neuron should contain the putative NT and be able to synthesize it
- Release
- The putative NT should be released on stimulation of the presynaptic axons
- Identity of action
- Application of the putative NT to the postsynaptic cell should reproduce the effects of normal transmission
- Pharmacology
- The action of a putative NT and the effect of presynaptic nerve stimulation should e altered in the same way by antagonists (eg acetylcholine on NMJ => EPSP | Curare drug inhibit ACh)
- Inactivation
- There should be a mechanism for inactivation of the NT (uptake or metabolism)
- Behavioural criteria
- Drugs which affect NT systems should have observable effects on whole animal
- (eg GABA → inhibit CNS)
- GABA blocker → Convulsions
- Drugs which affect NT systems should have observable effects on whole animal
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- Release
- Identity of action
- Pharmacology
- Inactivation
- Behavioural criteria
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- The presynaptic neuron should contain the putative NT and be able to synthesize it
-
Release
- The putative NT should be released on stimulation of the presynaptic axons
- Identity of action
- Application of the putative NT to the postsynaptic cell should reproduce the effects of normal transmission
- Pharmacology
- The action of a putative NT and the effect of presynaptic nerve stimulation should e altered in the same way by antagonists (eg acetylcholine on NMJ => EPSP | Curare drug inhibit ACh)
- Inactivation
- There should be a mechanism for inactivation of the NT (uptake or metabolism)
- Behavioural criteria
- Drugs which affect NT systems should have observable effects on whole animal
- (eg GABA → inhibit CNS)
- GABA blocker → Convulsions
- Drugs which affect NT systems should have observable effects on whole animal
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- Release
- Identity of action
- Pharmacology
- Inactivation
- Behavioural criteria
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- The presynaptic neuron should contain the putative NT and be able to synthesize it
- Release
- The putative NT should be released on stimulation of the presynaptic axons
-
Identity of action
- Application of the putative NT to the postsynaptic cell should reproduce the effects of normal transmission
- Pharmacology
- The action of a putative NT and the effect of presynaptic nerve stimulation should e altered in the same way by antagonists (eg acetylcholine on NMJ => EPSP | Curare drug inhibit ACh)
- Inactivation
- There should be a mechanism for inactivation of the NT (uptake or metabolism)
- Behavioural criteria
- Drugs which affect NT systems should have observable effects on whole animal
- (eg GABA → inhibit CNS)
- GABA blocker → Convulsions
- Drugs which affect NT systems should have observable effects on whole animal
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- Release
- Identity of action
- Pharmacology
- Inactivation
- Behavioural criteria
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- The presynaptic neuron should contain the putative NT and be able to synthesize it
- Release
- The putative NT should be released on stimulation of the presynaptic axons
- Identity of action
- Application of the putative NT to the postsynaptic cell should reproduce the effects of normal transmission
-
Pharmacology
- The action of a putative NT and the effect of presynaptic nerve stimulation should e altered in the same way by antagonists (eg acetylcholine on NMJ => EPSP | Curare drug inhibit ACh)
- Inactivation
- There should be a mechanism for inactivation of the NT (uptake or metabolism)
- Behavioural criteria
- Drugs which affect NT systems should have observable effects on whole animal
- (eg GABA → inhibit CNS)
- GABA blocker → Convulsions
- Drugs which affect NT systems should have observable effects on whole animal
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- Release
- Identity of action
- Pharmacology
- Inactivation
- Behavioural criteria
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- The presynaptic neuron should contain the putative NT and be able to synthesize it
- Release
- The putative NT should be released on stimulation of the presynaptic axons
- Identity of action
- Application of the putative NT to the postsynaptic cell should reproduce the effects of normal transmission
- Pharmacology
- The action of a putative NT and the effect of presynaptic nerve stimulation should e altered in the same way by antagonists (eg acetylcholine on NMJ => EPSP | Curare drug inhibit ACh)
-
Inactivation
- There should be a mechanism for inactivation of the NT (uptake or metabolism)
- Behavioural criteria
- Drugs which affect NT systems should have observable effects on whole animal
- (eg GABA → inhibit CNS)
- GABA blocker → Convulsions
- Drugs which affect NT systems should have observable effects on whole animal
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- Release
- Identity of action
- Pharmacology
- Inactivation
- Behavioural criteria
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- The presynaptic neuron should contain the putative NT and be able to synthesize it
- Release
- The putative NT should be released on stimulation of the presynaptic axons
- Identity of action
- Application of the putative NT to the postsynaptic cell should reproduce the effects of normal transmission
- Pharmacology
- The action of a putative NT and the effect of presynaptic nerve stimulation should e altered in the same way by antagonists (eg acetylcholine on NMJ => EPSP | Curare drug inhibit ACh)
- Inactivation
- There should be a mechanism for inactivation of the NT (uptake or metabolism)
-
Behavioural criteria
- Drugs which affect NT systems should have observable effects on whole animal
- (eg GABA → inhibit CNS)
- GABA blocker → Convulsions
- Drugs which affect NT systems should have observable effects on whole animal
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- Release
- Identity of action
- Pharmacology
- Inactivation
- Behavioural criteria
Describe how each of the criteria for a neurotransmitter are defined:
- Presence and synthesis
- The presynaptic neuron should contain the putative NT and be able to synthesize it
- Release
- The putative NT should be released on stimulation of the presynaptic axons
- Identity of action
- Application of the putative NT to the postsynaptic cell should reproduce the effects of normal transmission
- Pharmacology
- The action of a putative NT and the effect of presynaptic nerve stimulation should e altered in the same way by antagonists (eg acetylcholine on NMJ => EPSP | Curare drug inhibit ACh)
- Inactivation
- There should be a mechanism for inactivation of the NT (uptake or metabolism)
-
Behavioural criteria
- Drugs which affect NT systems should have observable effects on whole animal
- (eg GABA → inhibit CNS)
- GABA blocker → Convulsions
- Drugs which affect NT systems should have observable effects on whole animal
Which receptors have a NT binding site that is intrinsic to the ion channel protein?
Ionotropic Receptors
GABAA
Nicotinic ACh
In ________ receptors, the NT interacts directly with the ion channel
In ionotropic receptors, the NT interacts directly with the ion channel
Ionotropic receptors are involved in the generation of _________
Ionotropic receptors are involved in the generation of fast epsp’s and ipsp’s
Ionotropic receptors involve increases in _________ to ____ or _____
Ionotropic receptors involve increases in conductance to anions or cations
NT binds channel mol → channel opens → Pos in = depol | Neg in = hyperpolarization | Neg out = depol | Pos out = hyperpol
Five examples of ionotropic receptors:
- Nicotinic ACh
- GABAA
- Glycine
- 5-HT3 (serotonin)
- NMDA, AMPA, and Kainate receptors for glutamate (excitatory ion channels)
Binding site of metabotropic receptors?
Binding site remote so information from the NT binding site is “transduced” via G-proteins and sometimes via second messenger systems
With metabotropic receptors, neurotransmitter interacts ______ with the ion channel
With metabotropic receptors, neurotransmitter interacts indirectly with the ion channel
Metabotropic receptors are involved in _______ effects
Metabotropic receptors are involved in neuromodulatory effects
Activation of metabotropic receptors often leads to decreases in ______ of _______
Activation of metabotropic receptors often leads to decreases in conductance of K+ or Ca2+ channels
→ electrical effects => more often close (reduce conductance)
Because NT’s of metabotropic receptors activate second messenger systems - can orchestrate a change in the physiological status of the ___________
NT can affect a variety of _____, _____, _____ and ______
Because NT’s of metabotropic receptors activate second messenger systems - can orchestrate a change in the physiological status of the postganglionic neuron (pleiotropic action)
NT can affect a variety of ion channels, ion pumps, enzymes and gene expression
What are four examples of metabotropic receptors?
- Muscarinic ACh receptor
- alpha and beta adrenoceptors (NE/E)
- Metabotropic aminoacid receptor
- Peptide receptors
Some neurotransmitters such as ____, ___, ____ and _____ act at both ionotropic and metabotropic receptors
Some neurotransmitters such as ACh, GABA, Glutamate, and 5-HT act at both ionotropic and metabotropic receptors
_______ and _______ work only on metabotropic receptors
peptides and catecholamines work only on metabotropic receptors
→ no ionotropic receptors for peptides
How can nt’s change the activity of neurons over prolonged periods?
- Seconds or minutes in the case of slow synaptic responses or Ca2+ channel modulation
- Almost permanently following alterations of gene expression
4 ways to inactivate neurotransmitter:!@
- Enzymatic (eg cholenesterase → Ach)
- Uptake into presynaptic terminals or glial cells (Reuse/recycle)
- Diffusion
- Receptor desensitization
What happens at autoreceptors?
Receptors on presynaptic membrane
Released transmitter feeds back on presynaptic terminal → inhibits own release of presynaptic Ca++ by inhibiting presynaptic Ca++ channels
Provide an example of autoregulation
Noradrenaline from sympathetic neuron also acts on presynaptic membrane of parasympathetic neuron to alter ACh release
Nicotinic receptors are blocked by ______ and ________
- Nicotinic receptors are blocked by d-tubocurarine and _alpha-bungarotoxin (_snake toxin)
Muscarinic receptors are blocked by ________
Muscarinic receptors are blocked by Atropine
What are the five Muscarinic receptor subtypes?
M1, M2, M3, M4, M5
Where are nicotinic synapses located?
- Neuromuscular junction
- Autonomic ganglia (SNS/PNS)
- Brain and Spinal cord (all nerves leaving CNS release ACh)
Where are Muscarinin synapses located?
- Parasympathetic neuroeffectors
- Brain and Spinal Cord
What enzyme is involved in synthesis of Acetylcholine ACh?
Chat/CAT - Choline-acetyltransferase
What enzyme inactivates ACh?
AChE - Acetylcholinesterase
______ is taken up by presynaptic terminal for re-synthesis of ACh
Choline is taken up by presynaptic terminal for re-synthesis of ACh
What happens if anticholesterases are introduced to the system?
Anticholinesterases inhibit cholinesterase
→ unable to breakdown ACh => excess ACh stops heart
How is ACh related to alzheimers?
ACh plays a role in memory
Some central cholinergic neurons are lost in Alzheimer’s disease
ACh can be found in cell bodies in the ____ and ______ and travel to spinal motoneurons
ACh can be found in cell bodies in the septum and nucleus basalis and travel to spinal motoneurons
ACh can be found in cell bodies in the septum and nucleus basalis and travel to __________
ACh can be found in cell bodies in the septum and nucleus basalis and travel to spinal motoneurons
____ is the go between of NS and mm
ACh is the go between of NS and mm
Noradreneline/Norepinephrine acts on which two receptors?
- Alpha and beta receptors
- GPCR’s
Which NT is the main sympathetic neuroeffector?
Noradrenaline/Norepinephrine
Noradrenaline acts on ______ ; cell bodies in _______
Noradrenaline acts on brain and spinal cord ; cell bodies in Locus Coeruleus
How is norepinephrine synthesized?
In the cytoplasm:
- Tyrosine is converted to Dopa by tyrosine hydroxylase
- Dopa is converted to Dopamine by Dopa decarboxylase
- Dopamine enters synaptic vesicle
In Synaptic Vesicle:
- Dopamine is converted to Norepinephrine by dopamine beta-hydroxylase
How is Norepinephrine inactivated? (2)
- Uptake 1 into presynaptic terminal
- Reused or inactivated by monoamine oxidase
- Uptake 2 into postsynaptic neuron or tissue
- Metabolized by Catechol-o-methyltransferase
What happens to norepinephrine that is taken into the presynaptic terminal?
It is reused or inactivated by monoamine oxidase
What happens to Norepinephrine that is taken up into the postsynaptic neuron or tissue?
It is metabolized by Catechol-o-methyltransferase
What are two examples of pharmacological blockers of noradrenaline uptake (potentiate actions of noradrenalin)
Cocaine
Some antidepressants
An example of a pharmacological method that blocks the inactivation of norepinephrine?
Monamine oxidase inhibitors
Recall: monoamine oxidase inactivates norepinephrine that is taken back into the presynaptic vesicle
Dopamine receptors are present in cell bodies in the _________, ______ and ________
Dopamine receptors are present in cell bodies in the Substantia nigra, Ventral tegmental area and Arcuate nucleus of hypothalamus
5 dopamine receptors?
D1, D2, D3, D4, D5 - GPCR’s
Loss of dopaminergic neurons in ______ pathway leads to Parkinson’s Disease
Loss of dopaminergic neurons in nigral-striatal (substantia nigra) pathway leads to Parkinson’s Disease
Which pathway is dopamine involved in in the ventral tegmental area?
mesolimbic pathway
What is the pathway of dopamine in the substantia nigra?
Nigrostriatal pathway
The ________ pathway (DA) is involved in addiction and reward
The Mesolimbic (ventral tegmental area) pathway (DA) is involved in addiction and reward
dopamine receptor _______ are used to treat psychosis - act in ______ pathway
dopamine receptor antagonists are used to treat psychosis - act in mesolimbic (ventral tegmental area) pathway
How does cocaine potentiate dopamine?
Blocks its uptake - contributes to its euphoric effect in mesolimbic pathway (ventral tegmental area)
What are the four serotonin (5-HT) receptors. What type of receptors are they?
- 5-HT1
- 5-HT2
- 5HT4
- 5-HT7
G-protein coupled (metabotropic)
Which dopamine receptor is a cation channel?
5-HT3
Serotonin cell bodies in ______
Serotonin cell bodies in Raphe nuclei
Serotonin has a peripheral role in _________
Serotonin has a peripheral role in enteric nervous system
Pharmacology aspect of serotonin (5-HT)
Selective serotinin reuptake inhibitors (SSRIs) such as fluoxetine (prozac) used in depression
GABA is a major ______ neurotransmitter
GABA is a major inhibitory neurotransmitter
Inhibition of effects of GABA (with ______) produce _______
Inhibition of effects of GABA (with bicuculline) produce convulsant effects
GABAa - _______ channel
GABAa - Cl- channel (ionotropic)
GABAb - _______ receptor
GABAb - G-protein coupled receptor (metabotropic)
GABAa receptor channel has binding sites for _______, ______, certain _____ and other ________ drugs (potentiate GABA action)
GABAa receptor channel has binding sites for benzodiazepines (diazepam etc), barbiturates, certain steroids and other sedative-hypnotic, anxiolytic or anticonvulsant drugs (potentiate GABA action - calm things down)
*EtOH acts on gaba receptors
______ activates Cl- channels to act as an inhibitory neurotransmitter esp in spinal cord
glycine activates Cl- channels to act as an inhibitory neurotransmitter esp in spinal cord
Effects of glycine are blocked by ______
Effects of glycine are blocked by strychnine
Strychnine interacts with an ionotropic receptor (Cl-) to cause painful convulsions (laxative effect)
Glutamate is an _____ neurotransmittor
Glutamate is an excitatory (acidic) aminoacid neurotransmittor
What three ionotropic receptors does glutamate act on?
NMDA
AMPA
Kainate
What metabotropic receptors does glutamate act on?
G-protein coupled
NMDA receptors require ______ or _____ for activation
NMDA receptors require glycine or D-serine for activation
NMDA receptors are blocked by _____
NMDA receptors are blocked by Mg2+
NMDA receptors have a binding site for _________
NMDA receptors have a binding site for dissociative anesthetics (NMDA antagonists) eg ketamine
Neuropeptide Y controls:
appetite and blood pressure
Two endogenous peptides that mimic opioids
Enkephalins and Endorphins
Which neuropeptide is involved in pain transmission?
Substance P
All neuropeptides interact with ______ receptors
All neuropeptides interact with G-protein receptors
Activation of GABAa receptors:
a) leads to G-protein activation
b) produces a change in membrane potential by the opening chloride channels
c) Produces responses that can be blocked by benzodiazepines
d) Produces responses that are blocked by low concentrations of strychnine
e) Potentiates the action of glutamate at NMDA receptors
Activation of GABAa receoptors:
a) leads to G-protein activation (Cl- channel)
b) produces a change in membrane potential by the opening chloride channels
c) Produces responses that can be blocked by benzodiazepines (potentiates GABA action)
d) Produces responses that are blocked by low concentrations of strychnine (glycine effects blocked by strychnine)
e) Potentiates the action of glutamate at NMDA receptors (glycine or D-serine allow NMDA receptors to be activated)
Which of the following enzymes would be found in noradrenergic nerve terminals but not in dopaminergic nerve terminals?
a) Tyrosine hydroxylase
b) Dopa decarboxylase
c) Dopamine beta hydroxylase
d) Choline acetyl transferase
e) Phenylethanolamine N methyl transferase
Which of the following enzymes would be found in noradrenergic nerve terminals but not in dopaminergic nerve terminals?
a) Tyrosine hydroxylase
b) Dopa decarboxylase
c) Dopamine beta hydroxylase - converts dopamine to norepinephrine
d) Choline acetyl transferase
e) Phenylethanolamine N methyl transferase
Which of the following statements is true?
a) Administration of cocaine to a patient with Parkinson’s disease could theoretically worsen their symptoms
b) Atropine might be useful in reducing some of the effects of nerve gas poisoning
c) Serotonin is exclusively a CNS NT and has no important actions outside of the brain
d) Atropine is of great value in the tx of Alzheimer’s disease
e) All glycine receptors are g-protein coupled
Which of the following statements is true?
a) Administration of cocaine to a patient with Parkinson’s disease could theoretically worsen their symptoms - cocaine potentiates dopamine - loss of dopaminergic neurons in nigral-striatal pathway leads to parkinsons
b) Atropine might be useful in reducing some of the effects of nerve gas poisoning - blocks muscarinic receptors of ACh - excess ACh involved in nerve gas poisoning
c) Serotonin is exclusively a CNS NT and has no important actions outside of the brain - serotinin acts in enteric nervous system
d) Atropine is of great value in the tx of Alzheimer’s disease - cholinergic neurons are lost - atropine blocks muscarinic receptors (ACh)
e) All glycine receptors are g-protein coupled - glycine acts on Cl- receptors
Which of the following neurotransmitters interacts with an ion channel coupled receptor:
a) NPY
b) Noradrenaline
c) serotonin
d) Dopamine
e) Substance P
Which of the following neurotransmitters interacts with an ion channel coupled receptor:
a) NPY - GPCR
b) Noradrenaline - alpha and beta adrenergic receptors (GPCR)
c) serotonin
d) Dopamine - (GPCR)
e) Substance P - (GPCR)