Species and sex differences in the behavioral effects of cocaine in monkeys

These studies compare environmental, social and pharmacological variables on cocaine self‐administration in male and female rhesus (RM) and cynomolgus (CM) monkeys when similar schedules of reinforcement were used. When cocaine was available under fixed‐ratio schedules, female CM acquired cocaine reinforcement at lower doses than female RM. Consistent with these findings, when male monkeys self‐administered cocaine under a concurrent schedule with food pellets as the alternative, male CM required lower cocaine doses to achieve preference compared to male RM. In male and female RM, there were no apparent differences in acquisition of cocaine reinforcement. However, evidence for sex differences emerged under conditions in which environmental or pharmacological history was studied. Socially housed dominant female CM and socially housed subordinate male CM were more sensitive to cocaine reinforcement. In RM, prenatally cocaine exposed male monkeys were more vulnerable to cocaine reinforcement compared to controls, while females were not different. Studies combining molecular imaging with behavior will provide valuable insight into gene‐sex‐environment interactions.