Cold acclimation and resistance to ethanol-induced hypothermia.

The fall in core temperature induced by a fixed dose of ethanol (1 g x kg-1 i.p.) was an exponential function of the ambient temperature over the range 0-18 degrees C. In rats acclimated to 4 degrees C for 7 days the dose response curve relating the fall in body temperature to ethanol was markedly attenuated. The hypothermic effect of ethanol declined exponentially over 20 days of exposure to 4 degrees C and by the 20th day the fall was no greater than in saline injected controls. Blood ethanol concentrations were similar in acclimated and non-acclimated rats indicating that pharmacokinetic factors do not account for the altered responses. Although the time course of the development of resistance to the hypothermic effect of ethanol parallels that of cold acclimation to 4 degrees C, and the development of non-shivering thermogenesis, the attenuated drug effect does not appear to be due to the altered metabolic activity of brown adipose tissue. It is suggested that the modulation of the effect of ethanol in lowering the thermoregulatory set point results from central nervous system adaptation to the environmental thermal stress.