Biochemical and behavioral effects of acute ethanol in rats at different environmental temperatures.

The role of ethanol-induced hypothermia on some selected biochemical and behavioral parameters was evaluated. Rats were kept from 1 h before to 1 h after injection (saline or ethanol 2 g/kg, 20% solution IP) in an environment chamber at either 22 degrees C or 35 degrees C, and then tested behaviorally or sacrificed. Exposure of rats to a warm environment (35 degrees C) prevented the ethanol-induced hypothermia found in rats kept at 22 degrees C. Ethanol-treated rats kept at 35 degrees C had an attenuated increase in levels of free fatty acids and of corticosterone in plasma, suggesting that part of the ethanol-induced response may result from hypothermia rather than from ethanol itself. In addition, tyrosine levels were unexpectedly increased by 18% in intoxicated animals kept at 35 degrees C. By contrast, gross motor activity tested 1 h after injection was depressed more in animals kept at 35 degrees C than in those kept at 22 degrees C, and swim performance was impaired more at 5-20 min after treatment in animals not showing hypothermia. The greater behavioral impairment was not due to any debilitating effects of the warm environment since the saline control animals showed comparable activity to that of rats kept at 22 degrees C. We conclude that ethanol-induced hypothermia may influence and interact with other actions of ethanol.