F.: Discriminative stimulus effects of cocaine in squirrel monkeys: Involvement of dopemine receptor subtypes

The involvement of dopamine (DA) receptor subtypes in the discriminative stimulus effects of cocaine was investigated in squirrel monkeys trained to discriminate cocaine from vehicle using a two-lever choice procedure. Lever pressing was main-tamed under a 1 0-response fixed-ratio schedule of food pres-entation. In substitution tests, (-)-cocaine and its high-affinity analogs 2$-carbomethoxy-3$-(4-fluorophenyl)tropane (CFT) and 23-carbomethoxy-3fi-(4-chlorophenyl)tropane(CC engendered dose-related increases in the proportion of cocaine-appropriate responses. Full (97-1 00%) substitution for the training dose of cocaine was observed with all three drugs, the rank order of potency being: CCI> CFT> cocaine. DA agonists differing in selectivity for D and 02 receptor subtypes [6-chloro-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-[1 H]-3-benzazepine (SK