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| Question | Answer |
| Describe how GABA is synthesised | Glutamine is converted to Glutamate (via Glutanimase). Glutamate is converted to GABA (Via Glutamic Acid Decarboxylase) |
| Where would you find GABA in long projecting neurons? | From the striatum to the globus pallidus and the substantia nigra |
| How are the actions of GABA terminated? | Re-uptake into presynaptic terminals and glial cells by GABA transporters. |
| What is GABA broken down by? | GABA Transanimase |
| What products of the breakdown of GABA? | Succinic semialdehyde and Glutamate |
| How are succinic aldehyde and Glutamate broken down? | Succininc semialdehyde is broken down to succinate and by 'SSA dehyrdalase'. Glutamate is converted into glutamine by '2-oxoglutarate'. |
| What type of channel is a GABAa channel? | Ligand gated |
| Which ions flow through a GABAa channel? | Cl- |
| Where are GABAa channels found? | Postsynaptically |
| What type of channel are GABAb channels? | G protein coupled |
| Where are GABAb channels located | Pre and Post synaptically |
| What is the structure of a GABA receptor? | Pentameric |
| What is the most common combination of subunits? | 2a, 2b, 1y |
| How many different types of a, B and Y are there? | a1-a6 B1-B3 Y1-Y3 |
| Which are the most abundant of each subunit? | a1 B2 Y2 |
| Where do GABA, agonists and competitive antagonists bind? | At the aB interface |
| Where do Benzodiazepines bind? | At the ay interface |
| At which class of receptor (GABAa of GABAb) do barbiturates, neurosteroids, general anaesthetics and ethanol bind? | GABAa |
| Which class of y subunits are required for benzodiazepine sensitivity? | y2 |
| Which a subunits are insensitive to benzodiazepines? | a4 and a6 |
| What effect do benzodiazepines have if the GABAa receptor contains a a1 subunit? | Sedation and amnesia |
| If the GABAa receptor contains a2 or a3 subunits what effect do benzodiazepines have? | Anxiolytic |
| How many subunits does the GABAb receptor have? What are they? | 2 - GABAb1 and GABAb2 |
| What is the function of each subunit? | GABAb1 binds to GABA, GABAb2 binds to the G-protein |
| Which G protein is the GABAb receptor attached to? | Gi/o |
| What are the effects of the Gi/o protein activation? | BY subunit activates VG K+ channel, inhibits VG Ca2+ channel. a subunit decreases cAMP |
| Name a GABAb agonist? | Baclofen |
| What does Baclofen do? | Used to treat spasticity (hypertonia) Could be used to relieve withdrawal symptoms |
| Which is more important for preventing seizures? GABAa or GABAb? | GABAa |
| What two things are possible actions of GABAb antagonists? | 1) Not pro-convulsants 2) May enhance cognition |
| Which receptor subtype is responsible for which part of the current? | A) GABAa 'fast' response B) GABAb 'slow' ressponse |
| At which part of the neuron are GABA receptors most useful in relation to blocking the effects of GLUTAMATE receptors? | Closer to the soma. |
| What is the precursor to glycine? | Serine |
| What are the two different glycine transporters and where are they found? | GlyT1 (Astrocytes) GlyT2 (Glycinergic neurons of spinal cord, brain stem and cerebellum) |
| Where is Glycine a co-agonist? | NMDA glutamate receptors |
| Which ion passes through Glycine channels? | Cl- |
| What is the general structure of a glycine receptor and which subunits can it be composed of? | Pentameric a(1-4) B1 |
| What are the most likely combinations of subunits? | 2a/3B 3a/2B |
| What is Stychine? | Glycine antagonist which is a convulsant |
| What also potentiates Glycine receptors? | Modulators of GABAa (e.g. general anaesthetics and benzodiazepines) |
| What is HYPEREKPLEXIA What is it linked to? | Exaggerated startle response to tactile or acoustic stimuli. Mutations in genes for glycine receptor or proteins linked to glycine transporter |
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