Possible expression of a σ1 site in rat pheochromocytoma (PC12) cells

Abstract To examine the functional interaction between the σ binding sites and nicotinic acetylcholine receptors, we investigated the effects of various σ receptor ligands on nicotine-evoked Ca 2+ uptake in differentiated PC12 cells. The IC 50 values of σ receptor ligands tested in this uptake study did not correlate with their K i values in the [ 3 H]1,3-di(2-tolyl)guanidine ([ 3 H]DTG) binding to guinea pig brain reported by Rothman et al. (1991). To clarify further the binding characteristics of the σ binding sites on PC12 cells, we examined the effects of σ receptor ligands on [ 3 H] N,N -dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine HCl ([ 3 H]NE-100) binding to PC12 membranes. The K i values of the various drugs tested for [ 3 H]NE-100 binding site closely correlated with their K i values for the DTG site-1 reported by Rothman et al. (1991). This study showed that PC12 cells express σ 1 -like sites and the inhibitory effect of σ receptor ligands on the nicotine-evoked Ca 2+ uptake was not directly coupled with either the σ 1 or σ 2 sites.