GABA and GABA receptors in invertebrates

GABA is the major inhibitory transmitter at invertebrate synapses in both the central and peripheral nervous systems. The receptors for GABA are well characterised electrophysiologically in a wide variety of invertebrate organisms but their biochemical and pharmacological profiles are less well defined. In general invertebrate GABA receptors are less sensitive to bicuculline than are vertebrate GABA_A receptors. There is much evidence that invertebrate GABA_A receptors have benzodiazepine modulatory sites but their pharmacological profile is distinct from that of vertebrate GABA_A receptors. The insect neuronal GABA_A receptor has been identified as the site of action of the cyclodiene insecticides and the avermectins may also act on these receptors. Molecular cloning experiments now in progress will reveal the detailed relationships between the invertebrate receptors and their mammalian counterparts.