Comparison of thyrotropin-releasing hormone with melanocyte-stimulating-hormone-release-inhibiting factor as pentobarbital antagonists in monkeys.

Thyrotropin-releasing hormone (TRH), 0.1 mg/kg, i.m., significantly counteracted pentobarbital narcosis in six monkeys, but melanocyte-stimulating-hormone-release-inhibiting factor (MIF), 0.1 mg/kg i.m., did not. Earlier dose-response studies in unanesthetized monkeys had shown that this dose of MIF stimulated motor activity; this dose of TRH had shown no stimulant effect, but a higher dose depressed activity. Thus, an MIF dose that stimulates unanesthetized monkeys does not reverse pentobarbital narcosis; a TRH dose that by itself is neither stimulant nor depressant does partially reverse pentobarbital narcosis.