Temperature dependence of ethanol lethality in mice.

The present study provides systematic evidence indicating a direct relationship between environmental temperature, rectal temperature and ethanol lethality. Male, C57 BL/6J mice, previously housed at room temperature (23 +/- 1 degree C), were injected intraperitoneally with 4.8 to 9.2 g kg-1 ethanol and then exposed for 24 h to ambient temperatures that did not appreciably exceed the thermally neutral range for sober mice (20 to 35 degrees C). There was a direct relationship between temperature and ethanol lethality at 8 and 24 h after injection. The 8 h LD50 increased by 64%, from 5.3 to 8.7 g kg-1, as environmental temperature decreased from 35 to 20 degrees C. The 24 h LD50 increased by 51%, from 5.3 to 8.0 g kg-1, across this temperature range. Each 5 degrees C reduction in ambient temperature induced a significant decrease in the rectal temperature of ethanol-injected mice. Mean rectal temperature ranged from 2.2 degrees C above baseline at an ambient temperature of 35 to 15 degrees C below baseline in the 20 degrees C environment. Ethanol induced a significant dose-related hypothermia in mice exposed to the 20, 25 and 30 degrees C environments but did not produce hypothermia in animals kept in the 35 degrees C environment. These findings indicate that the potency of potentially lethal ethanol doses varies with body temperature in accordance with partition and membrane expansion-fluidization theories of anaesthesia.