GABA Flashcards
Is GABA inhibitory or excitatory?
Inhibitory
GABA is inactivated by which reuptake molecules?
GAT
GABA is synthesised from glucose from the:
Krebs cycle
What enzyme synthesises GABA from glutamate?
GAD
What are the vesicular transporters called?
VGAT
Some GABA is transported by VAT into glial cells, what happens with the rest?
Taken back up by presynaptic terminal, metabolised into succinic aldehyde by GABA-T and recycled back into the krebs cycle
What is the product of the krebs cycle which is converted into glutamate
alpha ketoglutarate
GABA neurones are localised discretely, true or false?
False (found all throughout the brain in the cerebellum, hippocampus, hypothalamus, cortex., basal ganglia)
When excitatory glutamate and inhibitory GABA fire at the same time, is the threshold for an action potential reached?
No - local depolarisation (GABA balances glutamate)
What are the two types of GABA receptors?
GABAa (ionotropic) and GABAb (metabotropic)
Is GABAa responsible for fast or slow inhibition?
Fast
Where can GABAa receptors be found?
Postsynaptically
Where can GABAb receptors be found?
Both post and pre
What ions do GABAa receptors control?
Cl-
What do GABAb receptors control?
K+, Ca2+ (can inhibit neurotransmitter release)
How many subunits are in a GABA receptor?
5 (each made up of 4 transmembrane segments)
Which transmembrane segment lines the ion channel pore?
2 (TM2)
How many GABA binding sites are there on GABA receptors
2
Other than GABA, what is its GABAa receptor agonist?
muscimol
What are the GABAa receptor antagonists?
bicuculline, gabazine
Other than GABA, what is a GABAb agonist?
baclofen
What are the antagonists of GABAb?
2-hydroxy saclofen, CGP55845A
Does GABAb (the alpha subunit) inhibit or activate adenylyl cyclase?
inhibit
Presynaptic GABAb couple to which ion channels?
Ca2+
Postsynaptic GABAb couple to which ion channels?
K+
Postynaptic GABAb opens or closes K+ channels and this leads to…
Opens, slow hyperpolarisation (inhibitory effect)
Presynaptic GABAb opens or closes Ca2+ channels and what does this cause?
Closes, inhibits neurotransmitter release
How many GABAb units are required to make a functional GABAb receptor?
2 (GABAb R1 and GABAb R2)
Which unit of the GABAb receptor does GABA bind to?
GABAb R1
Which unit of the GABAb receptor is coupled to the G protein?
GABAb R2
What is used for muscle spasms and how does it work?
GABAb agonist baclofen, activates postsynaptic GABAb receptors in motor neurones
What is used for epilepsy and how does it work?
GABAb antagonists (e.g. 2-hydroxy saclofen, CGP 55845A) which increase GABA release and therefore synaptic inhibition
What effects do GABAb receptor agonist and antagonists have as drugs?
They are sedatives, baclofen is anxiolytic
