title: (+/-)Tetrahydroanisocycline and (+/-)tetrahydropalmatine binding to D1 and D2 dopaminergic receptors in human putamen.
abstract: D1 and D2 dopaminergic receptors were detected in membranes from human putamen by the specific binding of the radiolabelled antagonists [(3)H]SCH 23390 and [(3)H]spiperone, respectively. Competition binding experiments with plant alkaloids isolated from Anisocycla cymosa and their hydrogenated derivatives showed the same order of affinities for both receptor types, i.e. (+/-)tetrahydropalmatine > (+/-)tetrahydroanisocycline > anisocycline > remrefidine. Hydrogenation of anisocycline produced a more pronounced increase in affinity for the D1 receptors (27-fold) than for the D2 receptors (1.5-fold). The affinities of (+/-)tetrahydropalmatine and chlorpromazine were similar for the D1 receptors (K(i) = 0.42 and 0.30 ?M, respectively) but the alkaloid's affinity was appreciably lower for the D2 receptors (K(i) = 0.77 and 0.06 ?M, respectively).
authors.affiliation: Department of Protein Chemistry, Institute of Molecular Biology, Free University Brussels (V.U.B.) Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Vauquelin
authors.forename: J
authors.initials: J
authors.lastname: De Keyser
authors.forename: B
authors.initials: B
authors.lastname: Kanyinda
authors.forename: M
authors.initials: M
authors.lastname: Vanhaelen