[3H]Epibatidine binding to bovine adrenal medulla:: evidence for α3β4*nicotinic receptors

In these studies, [H-3]epibatidine is used as the radioligand to characterize nicotinic acetylcholine receptors (nAChRs) from bovine adrenal medulla. Specific binding reaches equilibrium within 30 min, and is saturable with a K-d value of 0.5 nM. The affinities of several cholinergic agents were determined, including nicotine (K-i, 0.2 muM), cytisine (K-i, 0.4 muM), carbachol (K-i, 4.7 muM), dihydro-beta-erythrodine (K-i, 33.6 muM), D-tubocurarine (K-i, 0.4 muM), 1,1-dimethyl-4-phenyl-piperazinium (K-i, 0.8 muM), decamethonium (K-i, 234 muM) and methyllycaconitine (K-i, 1.3 muM). These values are similar to reported values for recombinant alpha3beta4 nAChRs in transfected cell lines. These studies demonstrate [H-3]epibatidine binding to an easily obtainable adrenal membrane preparation and support the characterization of adrenal nAChRs as alpha3beta4* nAChRs. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.