Effects of chronic cocaine administration on aggressive behavior in virgin rats.

Virgin Sprague-Dawley rats received subcutaneous injections of saline, 3.5, 7.5 or 15 mg/kg of cocaine, twice daily, for 20 consecutive days. Females were videotaped for 10 minutes in the presence of a male rat for assessment of aggression towards the intruder 2, 3, and 5 days following cessation of cocaine or saline administration. Oxytocin levels in discrete brain areas were assayed following behavioral testing, 5 days following cessation of cocaine or saline administration. The 30 mg/kg-dose group tended to have a lower frequency of fight attacks and aggressive postures compared to saline-treated controls across sessions. The frequency of most of the behaviors analyzed were represented by quadratic functions across time, such that the highest frequency of behavior occurred 2 days following the final injection with relatively less activity 3 and 5 days following cessation of saline or cocaine administration. The 30 mg/kg cocaine-treated group had significantly lower hippocampal OT levels than the 15 mg/kg group 5 days following cessation of cocaine or saline administration.