VENTILATORY AND METABOLIC RESPONSES TO COLD AND HYPOXIA IN CONSCIOUS RATS WITH DISCRETE HYPOTHALAMIC-LESIONS

We tested the hypothesis that hypothalamic nuclei involved in thermore gulatory control could represent a site of integration of the metaboli c and ventilatory response to cold and hypoxia. Electrolytic lesions w ere performed bilaterally under stereotaxic guide, either within the a nterior or posterior hypothalamic areas of adult rats. One week later, oxygen consumption ((V) over dot(O2)) and ventilation ((V) over dot E ) were measured in the conscious animals during warm (27 degrees C) or cold (12 degrees C) conditions, in normoxia (21% O-2) or hypoxia (10% O-2), and compared to measurements obtained in control rats, which we re either intact or sham-operated. (V) over dots(O2), (V) over dot E, and body temperature did not differ between lesioned and control rats during warm normoxia. In cold and hypoxia, singly or combined, (V) ove r dot E/(V) over dot(O2) was higher in the lesioned rats, because of h igher (V) over dot E. The differences in the cold were mostly confined to rats with anterior lesions, whereas differences in hypoxia were mo stly in rats with posterior lesions. We conclude that the integrity of the anterior and posterior hypothalamic areas is important for the pr oper coupling of metabolism and ventilation during cold or hypoxic sti muli. (C) 1998 Published by Elsevier Science B.V. All rights reserved.