Analysis of the solubilized nicotinic acetylcholine receptor of Drosophila melanogaster

Abstract

Nicotinic acetylcholine receptors (AchR) from various vertebrate organisms have been intensively investigated because of their significance for the control of ion permeability within the process of synaptic transmission [ 1,2]. The presence of a nicotinic choline@ system in the central nervous system of insects, although not yet conclusively demonstrated, is strongly supported by a series of findings: (i) Mutants for two metabolic enzymes of acetylcholine, choline acetyltransferase and acetylcholine esterase, produce neuroanatomical, electrophysiological and behavioural defects in Drosophila melanogaster [3]. (ii) a-Bungarotoxin (aBgt), a specific ligand for the nicotinic AChRs of vertebrates, binds to a component present in heads of Drosophila melanogaster [4-71 and Musca domestica [ 51, in brain tissue of the moth Manduca sexta [8] and in abdominal nerve cords of Periplaneta americana [9]. The binding fulfils the criteria of saturability , pharmacological specificity and tissue localization, as required for a nicotinic AChR [4-71. (iii) Electrophysiological evidence corroborates the biochemical and pharmacological studies. cwBgt blocks transmission at the central-nerve giant-fiber synapses in the terminal abdominal ganglion of Periplaneta [9]. This blockage is also exerted by isothiocyanate and nicotine at concentrations similar to those required for the inhibition of the [12’I]cuBgt binding to extracts from Periplaneta and Drosophila 191. These findings make it very plausible to assume the existence of cholinergic synapses in the central nervous