Effect of sodium pentobarbital on behavioral thermoregulation in rats and mice

Thermopreferendum of the rat: inter- and intra-subject variabilities

The thermopreferendum of male hooded rats was studied in a temporal thermal gradient. The preferred ambient temperature was found to be approximately 19 degrees C. In addition to the thermopreferendum, three other physiological functions (resting body temperature, daily food intake, and daily ambulatory activity) were each measured in eight rats for 8 days. Overall variability of the thermopreferendum data was higher than that of body temperature and food intake data but lower than the variability of ambulatory activity data. Coefficients of inter- and intrasubject variabilities were computed for each of the four variables. Inter-subject variability was equivalent in all variables, but intrasubject variability was smaller for thermopreferendum and activity than for food intake and core temperature. The thermopreferendum of 19 degrees C is consistent with previously published results but inconsistent with the available data on the thermoneutral zone of the rat (27-28 degrees C). The cause of this inconsistency remains to be determined.

Effect of alcohol on behavioral and autonomic thermoregulation in mice

Male, BALB/c mice were injected intraperitoneally with ethyl alcohol (ethanol) in dosages of 0, 0.03, 0.1, 0.3, 1.0, or 3.0 g/kg and then placed in a temperature gradient which permitted the measurement of preferred ambient temperature (Ta). The 3 g/kg dosage of ethanol resulted in a slight, but statistically equivocal, lowering of the preferred Ta during the first 30 min of placement in the gradient. A replication of this experiment using a higher sample size indicated that a 3 g/kg dosage of alcohol caused a statistically significant decrease in preferred Ta. In another experiment, BALB/c mice were treated with the aforementioned ethanol dosages while metabolic rate (MR), evaporative water loss (EWL), and colonic temperature were measured 60 min postinjection at Ta's of 20, 30, and 35 degrees C. At a Ta of 20 degrees C a dosage of 3 g/kg caused a significant decrease in MR, EWL, and colonic temperature. At a Ta of 30 degrees C this same dosage caused significant reduction in colonic temperature, however; at a Ta of 35 degrees C ethanol had no effect on these parameters. In conclusion, mice treated with a relatively large dose of ethanol will select a significantly cooler Ta, which is associated with hypothermia. These combined behavioral and autonomic thermoregulatory effects suggest that ethanol led to a decrease in the set-point body temperature.