The identification of GABA receptor binding sites in insect ganglia

The binding of [(3)H]muscimol to membrane fractions from central nervous tissue from fly (Musca domestica) and locust (Schistocerca gregaria) was measured. Specific saturable binding was observed with K(d)s of 10 nM (locust) and 40 nM (fly) and B(max) values of 20 fmol/mg protein (fly) and 60 fmol/mg protein (locust). Binding was Na(+)-independent and in locust tissue an additional Na(+)-dependent binding component was observed. Pharmacological properties of the binding sites in both species are consistent with a GABA receptor site rather than an uptake/transport site. We conclude that insect central nervous tissue contains receptors that show some similarities to the GABA receptor complex of mammalian brain.