A behavioural and biochemical comparison of dopamine receptor blockade produced by haloperidol with that produced by substituted benzamide drugs

Haloperidol inhibited dopamine (DA) mediated behaviours and induced pronounced catalepsy in rodents. Metoclopramide, sulpiride, sultopride, tiapride and clebopride, in general, also inhibited these behaviours but only clebopride induced marked catalepsy. Haloperidol displaced ³H-haloperidol and ³H-spiperone from striatal binding sites and inhibited DA stimulated cyclase from striatal and mesolimbic regions. In general, substituted benzamide drugs displaced labelled ligands, but did not inhibit adenylate cyclase. Elevations of striatal HVA produced by haloperidol and sulpiride, but not other benzamide drugs, were partially reversed by atropine. Hypophysectomy did not prevent the elevation of forebrain HVA produced by sulpiride and metoclopramide. Substituted benzamide drugs appear to act on cerebral DA receptors that are independent of DA-sensitive adenylate cyclase and are not balance by a cholinergic input.