Starvation suppresses sympathoadrenal medullary response to cold exposure in rats.

The effect of 2 days (55 h) of starvation on the functional state of the sympathetic nervous system (SNS) and adrenal medulla in male rats was evaluated in both normal (24 degrees C) and cold (4 degrees C) environments. Fasting (24 degrees C) significantly decreased NE turnover in heart and spleen, and the concentration of plasma epinephrine (E) and norepinephrine (NE). Cold exposure in the fed animals significantly increased NE turnover in the heart and plasma E, but had no effect on plasma NE or spleen NE turnover compared to normal (no stress) conditions. Cardiac NE turnover was 50% less in fasted cold-stressed animals than in fed cold-stressed animals. Plasma E remained at low levels. Plasma concentration of free fatty acids was significantly elevated in the fasted state in both warm and cold environments. These results suggest that 2 days of starvation in adult male rats suppresses the activity of the SNS and adrenal medulla and interferes with the normal adrenergic response to cold stress. Moreover, E appears not to be essential for mobilization of fat stores for energy metabolism in the fasted state in either warm or moderately cold environments.