The interactive effects of cocaine and imipramine on self-stimulation train-duration thresholds.

The present experiment examined the ability of the tricyclic antidepressant imipramine to influence cocaine's effect on intracranial self-stimulation. Following a predrug, saline injection period, cocaine hydrochloride (10, 20 or 30 mg/kg) was injected (IP) in 19 rats implanted with ventral tegmental area electrodes. Cocaine treatment uniformly decreased self-stimulation train-duration thresholds. In the next phase, the subjects were divided into two groups. One group received cocaine (as in the previous phase) and the other received cocaine plus imipramine (10 mg/kg, IP). Imipramine doubled cocaine's effect on self-stimulation train-duration thresholds. In addition, several other effects of cocaine (e.g., bradycardia, rear-limb dyskinesia) were potentiated by imipramine treatment. The results suggest that care must be exercised when treating cocaine abuse with tricyclic antidepressants since coadministration of these drugs intensifies cocaine's effects.