EVIDENCE THAT THE ABILITY OF IMIDAZOLINE COMPOUNDS TO STIMULATE INSULIN-SECRETION IS NOT DUE TO INTERACTION WITH SIGMA-RECEPTORS

Recent studies have suggested that a variety of ion channels possess a binding site for ligands such as phencyclidine (PCP), dizocilpine and certain a ligands and that some imidazoline compounds can also bind t o this site. We have investigated whether interaction with this bindin g site could account for the ability of imidazolines to stimulate insu lin secretion from rat islets. Neither PCP nor dizocilpine shared the insulin secretory activity of the imidazoline efaroxan in rat islets s uggesting that they do not have similar actions in the pancreatic B-ce ll. Further, we were able to define a new antagonist, KU14R (2 (2-ethy l 2,3-dihydro-2-benzofuranyl)-2-imidazole) which selectively blocks th e insulin secretory response to imidazolines. The results suggest that imidazolines do not stimulate insulin secretion by causing physical b lockade of the K+-ATP channel in pancreatic B-cells and show that thei r effects are not reproduced by PCP or a receptor ligands.