The effects of a shared history of drug exposure on social choice.

Selection theories of drug use propose that individuals choose or self-select into peer groups on the basis of perceived similarities with other group members with regard to their beliefs, attitudes, and histories of drug use. The purpose of the present study was to determine whether a shared history of drug exposure would influence choice of a social partner. Adolescent male rats were treated with either cocaine (3.0 mg/kg, intraperitoneally) or saline and their preference for a cocaine-treated rat or a saline-treated rat was measured in a partner preference test. Next, a series of conditioning trials were conducted in which rats were paired with a cocaine-treated and a saline-treated partner on alternating days for 10 days. Finally, a second partner preference test was conducted, in which preference for cocaine-treated and saline-treated partners was reassessed. Relative to baseline, rats showed an increase in the amount of time they spent with their similarly treated partner, and this effect was driven by cocaine-treated rats increasing the amount of time spent in proximity to their cocaine-treated partner after conditioning. These findings support a selection model of drug use by showing that a shared history of drug exposure is sufficient to establish a social preference for one individual over another.