Thermoregulatory effects of methanol in Fischer and Long Evans rats

While methanol neurotoxicity has been studied for decades, there are very few data available on the thermoregulatory effects of methanol exposure. This paper will present the results of three studies designed to assess the effects of methanol on body temperature and behavioral thermoregulation in Fischer and Long Evans rats. The first study measured the onset of body temperature changes following methanol exposure. Following gavage of 3 g/kg methanol (20% w/v in saline), brain temperature (Tbr) of Fischer rats decreased 1.5 degrees C within 35 min. A similar volume of saline led to transient increases in Tbr. A second study assessed the time course of changes in body temperature by measuring colonic temperature (Tc) hourly following IP injection of saline or 1 or 3 g/kg methanol. The highest dosage of methanol caused a significant hypothermia in both Fischer and Long Evans rats. The hypothermia reached its nadir in both strains at 1-2 hours and partially recovered within the 6 hour experiment. The third study measured the effects of methanol on behavioral thermoregulation. Fischer and Long Evans rats were gavaged with saline or 1-3 g/kg methanol and placed in a temperature gradient. After 90 min in the gradient, rats of both strains which received 2 or 3 g/kg methanol had a significantly lower Tc than control rats. However, the methanol-treated rats remained in the cool end of the gradient and did not prevent the hypothermic effect of the alcohol. The absence of an observed effect on behavioral temperature selection suggests that methanol may interfere with thermal sensation.