The action of conformationally restricted analogues of GABA on Limulus and Helix central neurones.

Intracellular recordings have been made from GABA sensitive neurones in the central nervous system of Limulus and Helix. The following conformationally restricted analogues of GABA all possessed GABA-like activity on Limulus neurones and Helix excitatory GABA receptors: muscimol, thiomuscimol, THIP, isoguvacine and piperidine-4- carboxylic acid. It is suggested that GABA interacts with these receptors in a partially extended and almost planar conformation.