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
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