Abuse‐related behavioral effects of ketamine in adult and adolescent rats

Abstract

The dissociative anesthetic ketamine has been subject to growing rates of abuse worldwide, particularly in adolescent populations. This project compared the behavioral effects of ketamine in place conditioning and intravenous self‐administration procedures in adolescent (PND 28–50) and adult (>;PND72) male Sprague Dawley rats. Cocaine served as a positive control. In the place conditioning study, 4 conditioning sessions following administration of 1, 3 or 10 mg/kg ketamine were counterbalanced with 4 sessions following saline administration. Preference was determined based on change in time spent in the drug‐paired environment. In the self‐administration assay, 0.03, 0.1 or 0.3 mg/kg/infusion of ketamine was evaluated for acquisition of self‐administration behavior and level of drug taking under a progressive ratio schedule. In the place‐conditioning assay, the 3 and 10 mg/kg ketamine produced aversion in the adults whereas adolescents demonstrated place preference for the 1 and 3 mg/kg doses. Conversely both age groups acquired self‐administration behavior at all doses of ketamine and cocaine. These divergent results for ketamine in the adults may reflect inherent differences in the two procedures. However, because cocaine produced evidence of hedonic effects in both age groups, it also suggests unique behavioral characteristics of ketamine and important differences in its effects based on age.