Rectal and brain temperatures in ethanol intoxicated mice.

The present study tested the assumption that deep rectal temperature reflects brain temperature in ethanol-intoxicated mice exposed to a range of ambient temperatures. Adult C57BL/6J mice were injected IP with one of three hypnotic doses of ethanol (3.2, 3.6, or 4.0 g/kg, 20% w/v) or with normal saline and were exposed to ambient temperatures of 15, 22, 32, or 34 degrees C. Thirty minutes post-injection, the mice were killed by cervical dislocation, decapitated and their rectal and brain temperatures were recorded simultaneously. Rectal and brain temperatures in the intoxicated mice increased significantly as the ambient temperature increased and were highly correlated and linearly related with each other. Although correlated, brain and rectal temperatures in these mice did not change in parallel, with brain temperatures increasing less rapidly than rectal temperatures. Additional studies indicated that similar relationships (correlated, but non-parallel) exist between the brain and rectal temperatures at 60, 120, and 180 min after injection of 3.6 g/kg ethanol. These findings suggest that rectal temperature can be used to quantify brain temperature in intoxicated mice, and extend to intoxicated animals evidence that brain temperature is controlled independently from rectal temperature.