Cholinergic binding sites with muscarinic properties on membranes from the supraoesophageal ganglion of the locust (Schistocerca gregaria)

A crude membrane preparation from the supraoesophageal ganglion of the locust (Schistocerca gregaria) shows specific binding of muscarinic cholinergic ligands. Analysis of the kinetics of binding reveals the presence of at least two binding sites with dissociation constants, K_d of 0.76 and 37.7 nM. The pharmacological profile of the higher affinity site is different from that seen for muscarinic receptor sites in mammalian brain.The binding sites reported here are quite distinct from nicotinic-like receptor sites in the same tissue and lend further support to suggestions that there are at least two types of acetylcholine receptors in insects.