Impulsivity and vulnerability to cocaine self‐administration in adult rhesus monkeys exposed to cocaine in utero

Abstract

Impulsivity is a trait that can be assessed as a predictor of increased likelihood to self‐administer drugs of abuse. A validated method to assess impulsivity is delay discounting, a model based on choice between different magnitudes of reinforcers under different delay conditions. In this study, male and female adult rhesus monkeys prenatally exposed to cocaine (n = 10) and controls (n = 11) chose between a small immediate reinforcer, one 1‐g banana‐flavored pellet, or a larger delayed reinforcer, three pellets. The delay varied between 0 and 300 s; conditions remained constant for at least 5 consecutive sessions. The delay value at which the monkey chose the immediate and delayed reinforcers equally often (the ED50) provided an index of impulsivity. Preliminary data indicate that monkeys exposed to cocaine in utero have a smaller mean ED50 value (70 s) than controls (110 s), indicating greater impulsivity. These differences were not correlated with cerebrospinal fluid levels of serotonin or its metabolite. Sex differences were observed as only the male prenatally cocaine exposed monkeys exhibited increased impulsivity. Whether this increased impulsiveness predicts a greater vulnerability to self‐administer cocaine is currently being examined. DA 25120, DA 13370.