3. GAMMA AMINO BUTYRIC ACID(GABA)
Major inhibitory neurotransmitter in
mammalian central nervous system
Present in the nerve terminal
Released from electrically stimulated
neurons
GABA functions by binding to specific
transmembrane present in plasma
membrane
6. STORAGE
Newly synthesized GABA is stored in synaptic
vesicle by means of vesicular transporter.
These are stored at postsynaptic terminal untill
action potential release.
RELEASE
o Stored GABA releases into synaptic cleft
stimulated by depolarisation of presynaptic
neurons.
o GABA diffuses across the cleft to target receptors
on postsynaptic surface.
o The action of GABA is terminated by reuptake of
GABA by presynaptic nerve terminals & glial cells
7.
8. RECEPTORS
GABA exerts its effects by two types of receptors
GABA A
GABA B
o They differ in their pharmacological &
biochemical properties
o GABA A is ionotropic & GABA B is metabotropic
o GABA receptors are channel receptors
9. GABA A RECEPTOR
It has pentameric
structure
It has structural
similarity & functional
similarity with ligand-
gated ion channels
Each GABA A receptor
subunit contains two
alpha subunit,two beta
subnit & one gamma
subnit
10. GABA B RECEPTOR
They are hetro dimers
Two GABA B subunits
have been cloned
b1&b2
B1 subunit has GABA
binding site,while B2
subunit interacts with g
protein
Two biological action:
• decreases ca
2+conductance
• increases k+
condctance