Unsaturated Analogues of the Neurotransmitter GABA: trans-4-Aminocrotonic, cis-4-Aminocrotonic and 4-Aminotetrolic Acids

Analogues of the neurotransmitter GABA containing unsaturated bonds are restricted in the conformations they can attain. This review traces three such analogues from their synthesis to their use as neurochemicals. trans -4-Aminocrotonic acid was the first conformationally restricted analogue to be extensively studied. It acts like GABA across a range of macromolecules from receptors to transporters. It acts similarly to GABA on ionotropic receptors. cis -4-Aminocrotonic acid selectively activates bicuculline-insensitive GABA C receptors. 4-Aminotetrolic acid, containing a triple bond, activates bicuculline-sensitive GABA A receptors. These findings indicate that GABA activates GABA A receptors in extended conformations and GABA C receptors in folded conformations. These and related analogues are important for the molecular modelling of ionotropic GABA receptors and to the development of new agents acting selectively on these receptors.