Physiol. Res. 53: 507-513, 2004


Clozapine Blocks Sympathetic and Thermogenic Reactions Induced by Orexin A in Rat

M. MONDA, AN. VIGGIANO, AL. VIGGIANO, F. FUCCIO, V. DE LUCA

Department of Experimental Medicine, Section of Human Physiology, Second University of Naples, Naples, Italy

Received August 4, 2003
Accepted November 3, 2003



Summary
This experiment tested the effect of clozapine on the sympathetic and thermogenic effects induced by orexin A. The firing rates of the sympathetic nerves to interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures were monitored in urethane-anesthetized male Sprague-Dawley rats before and for 5 h after an injection of orexin A (1.5 nmol) into the lateral cerebral ventricle. The same procedure was carried out in rats treated with orexin A plus an intraperitoneal administration of clozapine (8 mg/kg bw), an atypical antipsychotic that is largely used in the therapy of schizophrenia. The same variables were monitored in rats with clozapine alone. A group of rats with saline injection served as control. The results show that orexin A increases the sympathetic firing rate, IBAT and colonic temperatures. Clozapine blocks completely the reactions due to orexin A. These findings suggest that clozapine influences strongly the thermogenic role of orexin A. Furthermore, the remarkable hyperthermic role played by orexin A is confirmed.


Key words
Body temperature Clozapine Orexin A Rat Sympathetic activity


2004 by the Institute of Physiology, Czech Academy of Sciences