Neurotransmitters Flashcards
A neurotransmitter should be:
- present in presynaptic terminal
- released in response to stimulation
- able to interact with post-synaptic terminals
- rapidly removed from the synapse
What are the 5 steps of transmission?
1) Synthesis
2) Storage
3) Release
4) Post-transmission effects
5) Inactivation
What does a neurotransmitter need mechanisms for?
- Synthesis and/or storgae
- Release
- Receptors
- Transmitter removal
Size of amino acid and amine neurotransmitters and where are they stored/released?
Small molecules that are stored/released form synaptic vesicles
Size of peptide neurotransmitters and where are they stored/released?
Large molecules that are stored in secretory granules
What are peptide neurotransmitters stored in?
Secretory granules
What do peptide neurotransmitters activate?
Only activate G-protein coupled receptors
What are G-protein coupled receptors activated by?
Peptide, amino acid and amine neurotransmitters
What is Dale’s principle?
A single neurone has a single neurotransmitter
Is Dale’s principle correct? Give a reason
No, many neurones have both types of neurotransmitters
Which non-peptides are abundant in all cells?
Glutamate and glycine
The synthesis of what is localised to axon terminals by enzymes?
ACh, GABA and amines
The synthesis of Each, GABA and amines is localised to where and by what?
Axon terminals and by enzymes
What is the most common excitatory transmitter in the CNS?
Glutamate
Give examples of receptors that glutamate binds to
NMDA and AMPA
What is AMPA important in?
Fast transmission
What does the binding of glutamate to AMPA receptors trigger?
Na+ and K+ currents which produces an excitatory post-synaptic potential
What do NMDA receptors often co-exist with?
AMPA receptors
What kind of block do NMDA receptors have?
A voltage-dependent Mg2+ block
Which ion is involved in a voltage-dependent block of NMDA receptors?
Mg2+
At resting potential, are NMDA receptors blocked by Mg2+?
Yes, opens as membrane potential increases
What does a voltage-dependent block on NMDA receptors mean?
These receptors need to be indirectly activated by another transmitter
What is the most common inhibitory transmitter in the brain?
GABA (y-amino butyric acid)
Reaction to form GABA
Glutamate ——> GABA + CO2
Requires Glutamic acid decarboxylase
Which enzyme is used in the reaction to form GABA from glutamate?
Glutamic acid decarboxylase
What does GABA produce via GABA-gated Cl- channels?
ISPS
What would happen if there is too much GABA action?
Coma
What would happen if there is too little GABA action?
Seizure
3 methods of presynaptic inhibition
- One neurone inhibits another
- Autoinhibition (neurone inhibits itself)
- Disinhibition (neuron inhibits inhibitors)
What are anxiolytic drugs? What channels do they act on?
Anxiety-dissolving drugs. Act on GABA-gated Cl- channels
What other chemicals can stimulate a response from GABA-gated Cl- receptors?
Ethanol, benzodiazepine, barbiturate, neurosteroid
What do PET scans show in patients who suffer from panic attacks?
Loss of GABA A receptors
What are GABA A receptors?
GABA-gated Cl- channels
What system do opiates act in?
The endogenous opiate system
Which was discovered first: opiate antagonists or endogenous opiates? Give the name of which one
Opiate antagonist: Naloxone
How are opiates synthesised?
Formed in rough ER and packaged into secretory granules
What are the 3 main types of opiate receptors?
µ (mu), κ (kappa), σ (sigma)
Give examples of where many opiate receptors are found
- Spinal cord
- Periaqueductal grey
- Amygdal
- Frontal cortex
- Brain stem
Opiate receptors are coupled with what?
G-protein
What are the downsides of using opiates for therapeutic purposes?
Tolerance and dependence develops
What are some therapeutic uses of opiates?
Analgesia
Intestinal disroders
Antitussive
What is analgesia?
Reduction in the perception of and emotional response to pain
What are antitussives?
Cough suppressants
Where is most of the body’s serotonin produced?
In the GI tract
