Effects of cocaine and related drugs in nonhuman primates. II. Stimulant effects on schedule-controlled behavior.

The behavioral effects of cocaine were compared with those of several cocaine derivatives and structurally distinct drugs that inhibit monoamine uptake. Squirrel monkeys were trained to respond under a fixed-interval schedule of stimulus-shock termination, and dose-effect curves were determined by administering cumulative doses i.v. Among the cocaine congeners, (-)-cocaine, (+)-pseudococaine and 1 alpha H, 3 alpha, 5 alpha H-tropan-3-yl-3,5-dichlorobenzoate produced dose-related increases in response rate, whereas (-)-pseudococaine, (-)-benzoylecgonine and (-)-benzoylnorecgonine did not increase responding consistently over a 100-fold or greater range of doses. 1-(2-[bis(4-fluorophenyl)methoxy]ethyl)-4-(3-phenylpropyl)piperazine, which selectively inhibits uptake of dopamine, and mazindol, methylphenidate, nomifensine and bupropion, which inhibit uptake of dopamine as well as other monoamines, had behavioral effects similar to those of cocaine. In contrast, desipramine and citalopram, which selectively inhibit uptake of norepinephrine and serotonin, respectively, produced only dose-related decreases in response rate. The results combined with previous studies demonstrate a close correspondence between the potencies of 15 different drugs for producing cocaine-like behavioral effects and for displacing specifically bound [3H]cocaine in caudate-putamen. These findings are consistent with the view that the behavioral effects of cocaine and related drugs are linked to their actions at specific cocaine recognition sites associated with the dopamine uptake system.