Cocaine as a discriminative cue in rats: interactions with neuroleptics and other drugs

Rats were trained to discriminate between the effects of 4 mg/kg of cocaine HCl and saline (1 ml/kg) in a T-shaped maze. When the animals reliably differentiated the imposed training conditions (cocaine vs. no drug), test sessions were interspersed in between the regular training sessions. Test trials resulted in a median effective dose (ED50) of 1.6 mg/kg of cocaine, and the duration of the discriminable effects of cocaine in producing 50% cocaine-appropriate responding was 57.9 min postinjection. Pretreatment with neuroleptics (pimozide, haloperidol, and chlorpromazine), but not with propranolol, phenoxybenzamine, alpha-methyl-para-tyrosine, or physostigmine, attenuated the cocaine discrimination. Data are discussed with reference to previous results from amphetamine discriminations.