Behavioral thermoregulation in the rat following the oral administration of ethanol

To assess if ethyl alcohol (ethanol) causes a reduction in the set-point for control of body temperature, behavioral thermoregulatory responses in the Fischer rat were measured following a single oral administration of ethanol. In a preliminary study, five rats were given 3.0 g/kg ethanol dissolved in saline (20%; v/v) by gavage and placed in a longitudinal temperature gradient for 2 hr. The temperature gradient permitted the rats to behaviorally thermoregulate (i.e. select a thermal preferendum). The selected ambient temperature (Ta) in the temperature gradient was notably lower during the initial and final stages of the test period when compared to the response of rats administered similar volumes of saline. Colonic temperature upon removal from the gradient was approximately 1.0 degree C below that of the saline-treated animals. In a follow-up study, rats were placed in the temperature gradient for 1 hr for accommodation purposes. The rats were then gavaged with 0, 1.0 or 3.0 g/kg ethanol and placed back in the gradient for another 2 hr. Selected Ta was significantly reduced in the 3.0 g/kg group during the second hour post-ethanol exposure. The 1.0 g/kg dosage had little effect on selected Ta. As in the preliminary study, the colonic temperature of the rats in the follow up study given 3.0 g/kg was 1.0 degree C below that of the control at 2 hr post-injection. Because the 3.0 g/kg treated animals were significantly hypothermic and selected cooler Tas in the temperature gradient, it was concluded that ethanol exerted a lowering of the set-point for control of body temperature.