Thyrotropin releasing hormone potentiates the effects of imipramine on brain serotonergic system

Abstract

Daily administration of thyrotropin-releasing hormone (TRH) (20 mg/kg) for 10 days in 2 equally divided doses increased 5-hydroxytryptamine and/or 5-hydroxyindoleacetic acid levels in certain brain areas. Chronic imipramine treatment (10 mg/kg) for 10 days significantly decreased the levels of brain 5-hydroxytryptamine and 5-hydroxyindoleacetic acid. When TRH was administered concurrently with imipramine (10 mg/kg), this neuropeptide significantly potentiated the effects of imipramine on lowering of endogenous levels of 5-hydroxytryptamine (striatum, hypothalamus) and 5-hydroxyindoleacetic acid (striatum, midbrain, pons-medulla). Our data provide a possible neurochemical basis for the reported potentiation of tricyclic antidepressant action by TRH.