| Abstract: Animals exposed to uncontrollable aversive stimuli have subsequent difficulties learning escape (i.e., Learned Helplessness - LH). Antidepressant drugs, administered at shortly before escape training generally hinder LH, but little is known about the maintenance of this effect. This experiment explored the short- and long-term effects of imipramine on escape learning by rats exposed to uncontrollable electric shocks. Forty eight rats served, half of which was exposed to uncontrollable shocks while the other half remained in their homecages. After 24 hours, they were distributed in groups that received an injection of imipramine (6mg/kg), saline or no substance. The rats underwent two escape learning tests (30 minutes and 168 hours after the injection). Among the rats exposed to shocks, those treated with saline or no substance presented LH in both tests. Those treated with imipramine showed two types of result: most presented absence of LH, similar to experimentally-nave rats, whereas others presented LH. The effects of short- and long-term imipramine administration imipramine were similar. We discuss the drug effects based on different behavioral patterns produced by a history with uncontrollable shocks. |