GABA is the major inhibitory neurotransmitter in the mammalian central nervous system. It is synthesized in neurons and stored in synaptic vesicles until released into the synaptic cleft via calcium-dependent exocytosis. Upon binding to GABA receptors on postsynaptic neurons, GABA elicits inhibitory responses by increasing chloride ion conductance through ionotropic GABA-A receptors or by decreasing calcium conductance and increasing potassium conductance through metabotropic GABA-B receptors. GABA is then removed from the synaptic cleft via reuptake into presynaptic neurons and glial cells to terminate its action.

1. GABA
SYNTHESIS,RELEAS
E,
STORAGE,RECEPTO
R

2. HOW NEUROTRANSMITTER ACT…

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

4. o Molecular formula:C4H9NO2
o GABA is a zwitter ion with deprotonated
carboxy group and protonated amino group

5. SYNTHESIS OF GABA

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

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