Repeated imipramine enhances sensitivity of the brain dopaminergic system related to exploratory behavior.

The influence of imipramine treatment on apomorphine-induced behavior was studied. Imipramine was administered twice a day for 14 days at 10 mg/kg. The control group received a single dose of imipramine. Both groups were tested at 48 hours after imipramine administration, using open field; the number of line crossings and episodes of rearing and looking into holes were counted as part of the exploratory behavior. Repeated, but not single, administration of imipramine increased the exploratory activity induced by apomorphine injection an effect which was blocked by haloperidol pretreatment. The results indicate that repeated imipramine administration enhances the sensitivity of brain dopamine receptors related to exploratory behavior.