Multiple conductances of neuronal nicotinic acetylcholine receptors

In the presence of acetylcholine, cationic channels with three different conductances were recorded from neurones of the dissociated housefly (Musca domestica). Large conductance (80 pS) channels, resembling those that are abundant in reconstitution studies with a 65 kDa alpha-bungarotoxin affinity purified polypeptide, were detected in situ. The two larger conductance channels (80 pS; 32 pS) exhibited open and closed times that were best fitted by multiple exponential functions, indicating the presence of at least two open states. A third conductance (20 pS) showed brief, sparse openings and was least frequently observed. The 32 pS channel was the most common.