D1 receptor binding in rat striatum: modification by various D1 and D2 antagonists, but not by sibutramine hydrochloride, antidepressants or treatments which enhance central dopaminergic function

Abstract

[³H]SCH 23390 is a selective high affinity ligand for D₁ receptors in vitro. Using this ligand persistent blockade of D₁ receptors by SCH 23390 and cis-flupenthixol was shown to significantly increase the number of D₁ receptor binding sites in rat striatum. In contrast, repeated administration of the D₂-selective antagonist, clebopride, resulted in a small, but significant, reduction in number. No differences in binding affinity were observed and a single dose of these compounds was without effect. The D₂-selective antagonist, haloperidol, the non-selective D₁/D₂ receptor antagonist, chlorpromazine, the dopamine reuptake inhibitors, bupropion, GBR 12909 and nomifensine, and the dopamine releasing agent, d-amphetamine, had no effect on D₁ receptors. The antidepressant treatments, desipramine, zimeldine, amitriptyline, tranylcypromine, mianserin and ECS and the monoamine reuptake inhibitor, sibutramine, similarly did not alter striatal D₁ sites. Thus, of the treatments investigated only chronic receptor blockade by high affinity antagonists altered D₁ receptor binding in rat striatum.