GABA (FS - Week 2) Flashcards
Name 3 neurotransmitter criteria
- molecule must be synthesised and stored in presynaptic neuron
- once synthesised NT is taken up into vesicles and released from the presynaptic axon terminal upon stimulation
- molecules must produce a response in postsynaptic cells
What type of neurotransmitter is GABA?
major inhibitory in the CNS
What is GABA short for?
Gamma-aminobutyric acid
Name the steps of GABA synthesis
Glucose > Glutamate > *GABA
- by the enzyme Glutamate decarboxylase (GAD) and pyridoxal phosphate
Name the steps of GABA being transferred into vesicles
GABA >* Vesicles
- by the enzyme VIAAT (vesicular inhibitory amino acid transporters)
What type of vesicles is GABA stored in?
Oval
What type of vesicles is Glutamate stored in?
Round
What is pyridoxal phosphate derived from?
vitamin B6
The absence of this substance can lead to diminished amounts of GABA and as a result can cause seizures. Name that substance
vitamin B6
What is the transporter that reuptakes GABA
GABA re-uptake transporters (GATs)
Which enzyme is responsible for turning glutamate into GABA?
Glutamate decarboxylase (GAD)
Which GABA re-uptake transporter (GAT) sub-type is predominantly expressed on neurons?
GAT-1
Which GABA re-uptake transporter (GAT) sub-type is predominantly expressed on glial cells?
GAT-3
Which subunit interface comprises the GABAa receptor binding site for GABA?
alpha and beta
The GABAb receptor permits the efflux of which type of ion?
K+
Name the steps in the degradation of GABA
GABA > *Succinic semialdehyde > **succinic acid
- by the enzyme GABA transaminase (GABA-T)
** by the enzyme succinic semialdehyde dehydrogenase (SSADH)
What enzyme degrades GABA to Succinic semialdehyde?
GABA transaminase (GABA-T)
Name the two families of neurotransmitter receptors
- GPCRs (G-protein coupled receptors)
2. LGICs (Ligand-gated ion channels)
Explain the mechanism of action of ligand-gated ion channels.
- neurotransmitter binds and allow channel to open
- ions pass through the channel
- this increases or decreases the chance of an action potential firing - this depends on the type of neurotransmitter that binds
Explain the mechanism of action of GPCRs
- Neurotransmitter binds and activates molecular switches called G-proteins (comprised of a,B,Y subunits)
- these subunits dissociate and interact with ion channels or bind to other effector proteins e.g. enzymes
- this activates a secondary messenger pathway that opens or closes ion channels
What type of receptor is GABAa?
ionotropic/Ligand-gated ion channel
What type of receptor is GABAb?
Metabotropic/GPCR
What type of receptor is GABAc? Why is it different?
ionotropic/LGIC
it has a similar structure to GABAa but is insensitive to drugs that act at GABAa
The GABAa receptor permits the influx of which ion?
Cl-