Study of the pharmacological effects of harmidine in rats.

Various effects of harmidine hydrochloride, an alkaloid of Peganum harmalla, have been studied in rats treated with harmidine hydrochoride 12 mg/kg body weight alone and pretreated with pyridoxine. Harmidine produced shivering, ataxia, diarrhoea, reduction in motor activity, loss of postural reflex and hypothermia. Weight of animals, respiratory rate, heart rate, urinary output, oestrous cycle, leucocyte and red blood cell count, bleeding time, clotting time, haemoglobin and differential leucocyte count remained unaffected. Harmidine probably acts on the basal ganglia and brain stem reticular formation. The animals pretreated with pyridoxine did not show shivering, ataxia, reduction in motor activity, loss of postural reflex and hypothermia, indicating that harmidine probably acts by inhibiting the activity of pyridoxine in the brain. Thus protecting 5-hydroxytryptamine and norepinephrine of the brain from destruction by mono aminu-ry oxidase which needs pyridoxine as coenzyme for its activity (JPMA 30:88, 1980).