Amphetamine-haloperidol discrimination: effects of chronic drug treatment.
Rats responding for food reinforcement were trained in a 2-lever drug discrimination task. Groups of rats were trained to discriminate one of four doses of amphetamine (0.0, 0.1, 0.3, or 0.5 mg/kg) from haloperidol (0.02 mg/kg). Both the rate of acquisition and level of discrimination at asymptote were a function of amphetamine training dose. Following acquisition of this discrimination, choice behavior was assessed in the absence of drug during two test sessions. Twenty-four hours following the second drug-free test session, chronic drug treatment commenced. Half of the animals received 10 mg/kg amphetamine for 10 consecutive days while the other half received 1 mg/kg haloperidol during the same period. Choice behavior was assessed during three 2.5-minute unreinforced drug-free test sessions 24, 48, and 72 hours following the chronic drug regimen. Following chronic haloperidol, animals responded as though a small dose of amphetamine had been administered, while following chronic amphetamine, they responded as though a small dose of haloperidol had been administered. Collectively, these results suggest that animals trained to discriminate amphetamine from haloperidol respond on the basis of a continuum of dopaminergic function. Further, this continuum can be used to elucidate the net effect of pharmacologically-induced alterations in dopaminergic function, as well as the effect of nonpharmacological manipulations that may result in dopaminergic changes.
D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects; D003913:Dextroamphetamine / Q000494:pharmacology; D004192:Discrimination, Psychological / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005502:Food; D006220:Haloperidol / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012054:Reinforcement, Psychology / Q000187:drug effects; D013997:Time Factors
D000661:Amphetamine; D006220:Haloperidol; D003913:Dextroamphetamine