Sex difference in thermal preference of adult mice does not depend on presence of the gonads

Background: The thermoneutral zone (TNZ) is a species-specific range of ambient temperature (T-a), at which mammals can maintain a constant body temperature with the lowest metabolic rate. The TNZ for an adult mouse is between 26 and 34 degrees C. Interestingly, female mice prefer a higher Ta than male mice although the underlying mechanism for this sex difference is unknown. Here, we tested whether gonadal hormones are dominant factors controlling temperature preference in male and female mice. Methods: We performed a temperature preference test in which 10-week-old gonadectomized and sham-operated male and female C57BL/6J mice were allowed to choose to reside at the thermoneutral cage of 29 degrees C or an experimental cage of 26, 29, or 32 degrees C. Results: All mice preferred a Ta higher than 26 degrees C, especially in the inactive phase. Choosing between 29 and 32 degrees C, female mice resided more at 32 degrees C while male mice had no preference between the temperatures. Hence, the preferred T-a for female mice was significantly higher (0.9 +/- 0.2 degrees C) than that for male mice. However, gonadectomy did not influence the T-a preference. Conclusions: Female mice prefer a warmer environment than male mice, a difference not affected by gonadectomy. This suggests that thermal-sensing mechanisms may be influenced by sex-specific pathways other than gonadal factors or that the thermoregulatory set point has already been determined prior to puberty.