In the central nervous system, GABA is the main inhibitory neurotransmitter. GABA is a highly flexible molecule and, thus, can exist in many low‐energy conformations. Three major GABA receptors, termed GABAA, GABAB and GABAC receptors have been identified. GABAA and GABAC receptors are members of a superfamily of transmitter‐gated ion channels that include nicotinic acetylcholine, strychnine‐sensitive glycine and 5HT3 receptors. GABAA receptors are hetero‐oligomeric Cl– channels that are selectively blocked by the alkaloid bicuculline and modulated by steroids, barbiturates and benzodiazepines. 
A wide variety of GABAA receptor antagonists now exists. GABA receptor antagonists are drugs that inhibit the action of GABA. In general, these drugs produce stimulant and convulsant effects, and are mainly used for counteracting overdoses of sedative drugs. Examples include bicuculline, securinine and metrazol.
 M. Chebib and G. A. R. Johnston, “The ‘ABC’ of GABA receptors: A brief review,” Clin. Exp. Pharmacol. Physiol., vol. 26, no. 11, pp. 937–940, 1999, doi: 10.1046/j.1440-1681.1999.03151.x.