Differential antagonism by the antichlolinergic dexetimide of inhibitory effects of haloperidol and fentanyl on brain self-stimulation.

Haloperidol (0.08 mg/kg) or fentanyl (0.16 mg/kg) injected subcutaneously suppressed bar-pressing for brain-stimulation in rats, implanted with electrodes in the lateral hypothalamic area of the medial forebrain bundle. Increasing doses: 0.04, 0.16, 0.63 and 2.50 mg/kg of the central anticholinergic dexetimide gradually antagonized the haloperidol effects. The highest dose of dexetimide did not reduce the fentanyl-induced inhibition. The results, together with a literature survey on the anticholinergic effects on neuroleptic-induced catalepsy and inhibition of avoidance behavior, are related to biochemical findings and clinical effects.