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GABA signaling in brain


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GABA signaling in brain

GABA signaling in brain

Gamma-aminobutyric acid ( GABA ) is the most abundant inhibitoryneurotransmitter in the mammalian brain, where it is widely distributed.. GABAtransmission is present in the interneurons that modulate local neuronal circuitry,including noradrenergic, dopaminergic, and serotonergic neurons [1].

GABA in GABAergic terminals is formed from Glutamic acid in an enzymaticreaction mediated by Glutamic acid decarboxylases 1 and 2 ( GAD1 and GAD2), using pyridoxal phosphate as cofactor [2], [3]. After beingreleased into the synapses, GABA is inactivated by reuptake into presynapticterminals or into glial cells mediated by GABA transporters (GATs). GAT-1 isconsidered to be a neuronal transporter. GAT-2 and SLC6A11 (GAT-3) arebelieved to be glial transporters [1].

GABA is bound to GABAergic receptors. GABAergic receptors are represented bytwo main types, GABA-A receptor and Galpha(i)-specific GABA-B GPCRs, Thetwo types are characteryzed by different distribution on the surface of neurons.GABA-A receptor s are ionotropic and mostly postsynaptic receptors mainly locatedat the apical dendrite of the neurons, causing the fast inhibitory postsynapticpotential. It is essential for brain development and behavioral actions [4], [5]. Galpha(i)-specific GABA-B GPCRs may be localizatedon on presynaptic terminal soma and on postsynaptic neurone. Galpha(i)-specificGABA-B GPCRs are metabotropic receptors coupled to G-protein alpha-i family.Pre-synaptic Galpha(i)-specific GABA-B GPCRs inhibit neurotransmitter release bydown-regulating high voltage activated calcium channels, whereas postsynapticGalpha(i)-specific GABA-B GPCRs decrease neuronal excitability by activating aprominent inwardly rectifying potassium (Kir) conductance that underlies the lateinhibitory postsynaptic potentials. Not only implicated in synaptic inhibition but alsoin hippocampal long-term potentiation, slow wave sleep, muscle relaxation andantinociception [6].