d-Amphetamine and punished responding: the role of catecholamines and anorexia

Rats were trained to press a lever for food on a schedule in which components of variable interval reinforcement (V12') alternated with conflict components in which every response resulted in food delivery and footshock. Low doses of d-amphetamine selectively suppressed responding in the conflict component in a dose-dependent manner, whereas prefeeding suppressed responding in both components. Pretreatment with noradrenergic blocking agents (propranolol, phentolamine and phenoxybenzamine) did not diminish the suppressant effect of d-amphetamine, but this effect was reduced by pretreatment with alpha-methyl-para-tyrosine methylester and dopamine blockers (spiroperidol, haloperidol and clozapine) indicating that d-amphetamine was exerting its selective suppressant effect via the release of dopamine. It is suggested that the effects of low doses d-amphetamine on behaviour in conflict situations may provide a useful model for investigating the mode of action of neuroleptic drugs.