IDENTIFICATION AND CHARACTERIZATION OF IMIDAZOLINE-BINDING SITES FROMCALF STRIATUM

'Non-adrenoceptor'-binding sites for [H-3]clonidine (I-1-sites) and [H -3]idazoxan (I-2-sites) are identified in calf striatum membranes. The pharmacological profile of both subtypes was investigated by competit ion binding with the imidazolines idazoxan, cirazoline, Bu 224 (2-(4,5 -dihydroimidaz-2-yl)-quinoline) and Bu 239 (2-(4,5-dihydroimidaz-2-yl) -quinoxaline); the guanidino derivatives clonidine, moxonidine, guanab enz, amiloride and agmatine; the oxazoline rilmenidine and the imidazo le histamine. The competition experiments indicate that both populatio ns of imidazoline-binding sites in calf striatum consist of a high- (H ) and a low-affinity (L) compartment. The monoamine oxidase (MAO) inhi bitors pargyline (non-selective) and deprenyl (MAO-B-selective) have m icromolar affinity for the I-1-sites and much lower affinity for the I -2-sites. The venom of the marine snail Conus geographus is the most p otent of the 13 tested Conus venom preparations. None of the tested ve noms is able to discriminate between both sites.