This piece explains the function of the GABA-A receptor, a subtype of GABAminergic receptor involved in the action of a variety of depressant drugs.
|Diagram of the ligand gated|
GABA-A Recptor/Channel Complex.
Middle site: ion channel
Other sites: active and allosteric
Description: GABA-A (often referred to as the GABA-A receptor) is an inhibitory receptor complex located on the post synaptic membrane of neurons. It is composed of a ligand gated ion channel, and various binding sites on the extracellular surface - the sites consist of a primary site for GABA binding (which activates the gated ion channel), and allosteric sites (such as the benzodiazepine receptor) which modulate the function of the GABA binding site. These sites are distributed across five distinct subsects, which together form the extracellular surface of the GABA-A complex.
Function: GABA-A is but one subtype of the GABA receptor/complex, a major inhibitory device of the central nervous system. Activation of GABAminergic sites on the surface of post-synaptic neural membranes results in an inhibitory effect on its neurons; simply put, activation of GABAminergic sites reduces the sensitivity of nerve cells to respond to stimuli from other nerve cells.
Drugs and the GABA-A Complex: A variety of sedative-hypnotic, anxiolytic, and recreational drugs (alcohol, barbiturates, gabaxodal) target the GABA-A complex. Some of these agents target the main active receptor directly (thus activating the GABA-A complex by opening the ion channel), while others enhance the function of the active receptor indirectly. Benzodiazepine-type drugs produce their effects through the GABA-A complex. They do not agonize the active target site directly, but they act as positive allosteric modulators for GABA activity. They bind to allosteric sub-units of the GABA-A complex - their binding at these sites enhances the inhibitory action of this complex by changing the configuration of the target receptor, increasing its affinity for binding with the neurotransmitter GABA (gamma-amino butyric acid).