Juvenile desipramine reduces adult sensitivity to imipramine in two behavioral tests.

The behavioral effects of adult imipramine administration were examined in female rats treated with desipramine as juveniles (JDES), treated with saline as juveniles (JSAL), and untreated as juveniles (JUNT). In the forced swimming test, the juvenile groups displayed similar behavioral effects of imipramine when administered short term following a pretest forced swimming exposure. Similar effects of imipramine were observed when administered long term prior to the only test exposure. When rats were not given a pretest forced swimming test exposure, short-term imipramine had no effect on JDES rats but did influence JSAL and JUNT rats. In the open-field test, short- and long-term imipramine treatment affected the behavior of JUNT and JSAL rats. Short-term imipramine treatment influenced open-field behavior of JDES animals, but long-term imipramine treatment had no effect. These results suggest that JDES treatment may permanently alter the neural mechanism underlying the behavioral effects of antidepressant treatment.