Anxiety-like responses in adolescent rats following a 10-11-day withdrawal period from repeated cocaine administration

The present study was conducted to determine whether increases in anxiety-like behavior in adolescent rats repeatedly treated with cocaine would be observed following a withdrawal period of an intermediate length (i.e., more than 1 day but less than 2 weeks). Accordingly, rats were injected with either 10 or 20 mg/kg cocaine or with saline for 7-8 consecutive days followed by a 10-11-day drug-free recovery period at which time assessment in a zero maze was instituted. All animals were assessed in the zero maze twice with the two sessions being separated by 24 h of non-testing. The results indicated that all three groups spent equivalent amounts of time in the open portions of the maze on the initial test day. Group differences, however, emerged on the second test day with animals in both cocaine-treated groups spending significantly less time in the open portions of the maze relative to saline-injected control subjects. This was due to control animals increasing the amount of time spent in the open areas of the maze from the first to the second day of testing, an effect not observed in either of the two cocaine-treated groups. These data provide evidence that an anxiogenic-like response produced by repeated cocaine treatment in adolescent rats emerges after a relatively short withdrawal period.