Temperature dependence of ethanol depression in mice.

The relationship between environmental temperature, body temperature and ethanol depression was investigated in male C57BL/6J mice. Animals were injected with ethanol (3.6 g/kg) or saline and placed in an experimental or normal room temperature (control) environment. Environmental temperatures from 12-37 degrees C significantly influenced rectal temperature, sleep-time and wake-up brain ethanol concentrations. The rectal temperatures of ethanol-treated animals ranged from 1.5 degrees C greater to 11.3 degrees C lower than their matched saline controls, supporting indications that ethanol impairs normal thermoregulation. Sleep-time decreased up to 43% and wake-up brain ethanol concentrations increased as rectal temperature decreased from approximately 38-32 degrees C. More severe hypothermia after ethanol (rectal temperature less than 29 degrees C) increased sleep-time and decreased wake-up brain ethanol concentrations. These results indicate that sleep-time and brain sensitivity to ethanol vary with rectal temperature in accordance with predictions based on membrane expansion and partition theories of anesthesia and the anticipated anesthetic-like actions of severe hypothermia.