Adolescent impulsivity as a sex-dependent and subtype-dependent predictor of impulsivity, alcohol drinking and dopamine D2 receptor expression in adult rats
Impulsivity is a personality trait associated with a heightened risk for drug use and other psychiatric conditions. Because impulsivity-related disorders typically emerge during adolescence, there has been interest in exploring methods for identifying adolescents that will be at risk to develop substance use disorders in adulthood. Here, we used a rodent model to assess inhibitory control (impulsive action) and impulsive decision making (impulsive choice) during adolescence (43–50 days old) or adulthood (93–100 days old) and then examined the impact of development on these impulsivity traits by re-testing rats 50 days later. Impulsive action was not stable from adolescence to adulthood in male rats and was lowest in adult male rats, relative to adolescents and female rats. Impulsive choice was stable across development and unaffected by age or sex. Next, we examined the connection between our model of impulsivity and two measures relevant to substance abuse research: the initiation of voluntary alcohol drinking and dopamine D2 receptor (D2R) expression in the prelimbic prefrontal cortex. Consumption of saccharin-sweetened ethanol during 30-minute sessions in adulthood was associated with adolescent, but not adult, impulsive action, particularly in male rats. Prelimbic D2R expression was reduced in individuals with high levels of impulsive choice, and this relationship appeared to be strongest among female rats. The results of this study demonstrate that impulsive choice, along with its connection to D2R expression, is relatively unchanged by the process of development. For impulsive action, however, individual levels of impulsivity during adolescence predict drinking in adulthood despite changes in the measure during development.