Effects of psychotropic drugs on pressor and behavioral responses to brain stimulation in unrestrained, unanesthetized rats.

Electrical stimulation of the posterior hypothalamus (PH) and the mesencephalic reticular formation (MRF) in unanesthetized, unrestrained rats with chronic electrode implants and an arterial cannula elicited a rise in blood pressure accompanied by behavioral changes such as exploration, flight or escape responses. Pentobarbital inhibited both the pressor and behavioral responses to PH and MRF stimulation. Chlorpormazine, diazepam and imipramine depressed the pressor response to PH stimulation rather than that to MRF stimulation with affecting the behavioral responses. It is concluded from these results that chlorpromazine, diazepam and imipramine exert their action on the neural pathway involved in the pressor response rather than on that inducing behavioral responses, whereas pentobarbital affects more extended brain areas related to these neural systems.