Insect central nervous system gamma-aminobutyric acid.

Specific saturable binding of radiolabelled gamma-aminobutyric acid (GABA) has been demonstrated in central nervous system (CNS) extracts of the cockroach, Periplaneta americana. The pharmacological properties of these putative insect CNS GABA receptors differ from those of both the vertebrate GABAA and GABAB receptor sites. Autoradiographical techniques have been used to examine the localization of these [3H]GABA binding sites in a cockroach ganglion and have shown that they are found predominantly in the neuropile, the region where the majority of synaptic connections occur. The results suggest that these insect CNS [3H]GABA binding sites may represent a novel class of GABA receptors.