Presynaptic acetylcholine action at the locust neuromuscular junction

The application, in the bathing medium, of ACh (10⁻⁵ M) to the extensor tibiae nerve-muscle preparation of the locust caused a dosedependent increase in both the spontaneous and evoked release of transmitter and also modified the statistical characteristics of the spontaneous release process. ACh had no postsynaptic action. The effects of ACh on spontaneous transmitter release were dependent on extracellular calcium concentration and could be mimicked by carbachol, nicotine and acetyl-β-methylcholine and antagonised by D-tubocurarine and decamethonium. The results suggest the presence of cholinergic receptors on the nerve terminal of the locust neuromuscular junction.