Alcohol and heat tolerance in warm-acclimated rats

The effect of chronic ethanol intake and warm acclimation on the heat tolerance of rats under the influence of alcohol was studied. The animals were divided into two groups: Group 1 received water as their fluid intake and, group 2 received a 10% ethanol solution, and both groups were exposed to a temperature of 30 degrees C for 4 weeks. Excretion of urinary catecholamines was measured prior to warm exposure at 22 degrees C and once a week during warm exposure at 30 degrees C. After warm acclimation a dose of alcohol 2 g/kg was injected in the rats intraperitoneally (i.p.), and then they were exposed to a heat stress of 40 degrees C for 45 min. During warm acclimation, the controls consumed more fluid and they excreted more norepinephrine into the urine than the alcohol-fed animals during the first week. After the period of acclimation there were no significant differences in urinary excretion of catecholamines between the groups. Colonic temperature of the controls was 0.7 degrees C higher than in the alcohol-fed animals. Acute alcohol administration (2 g/kg) increased the colonic temperature of the alcohol-fed animals during a heat stress of 40 degrees C more than in the controls. After heat stress, the concentration of catecholamines in the blood was significantly higher in the controls. The results show that the hyperthermic effect of ethanol was more considerable in the rats whose drinking water during warm acclimation was an ethanol solution.