Autonomic thermoregulation after intermittent cooling of the spinal cord and cold exposure in the rat.

Abstract

O2 consumption and rectal [Tr] and skin [Tsk] temperatures were studied at various ambient temperatures [Ta] in unanaesthetized rats. These rats were thermally stressed for an average of 290 h either by prolonged and intermittent cooling of the spinal cord or by prolonged and intermittent exposure to an Ta. This induced the same increase in O2 consumption as did the thermal stimulation of the spinal cord. At all the test Ta, both groups of thermally stressed animals maintained a metabolic level higher than that of the controls. In the animals previously exposed to cold, the extent by which the metabolic rate was greater than that of the control animals was independent of Ta. In those previously subjected to cooling of the spinal cord, it increased as the Ta was lowered. Tr average Tsk were essentially unaffected by the treatments. Prolonged and intermittent cooling of the spinal cord increased the gain of the temperature control system, whereas prolonged and intermittent cold exposure has no effect on it. These forms of thermal stimulation are apparently not equivalent.