The present study characterized the relationship between brain temperature, rectal temperature, and ethanol sensitivity in the selectivity bred long-sleep (LS) and short-sleep (SS) mice. Radiotelemetric brain probe implanted and nonimplanted LS/lbg and SS/lbg male mice were injected with 2.5 and 4.9 g/kg ethanol, respectively, before exposure to ambient temperatures of 15 degrees C, 22 degrees C, or 34 degrees C. Ambient temperature significantly affected rectal temperature, brain temperature, and ethanol sensitivity, measured by impairment of righting reflex. Brain and rectal temperatures at return of righting reflex (RORR) were highly correlated. In SS mice brain and rectal temperatures at RORR were significantly positively correlated with loss of righting reflex (LORR) duration and significantly negatively correlated with blood ethanol concentration (BEC) at RORR. In LS mice rectal temperature at RORR was significantly negatively correlated with LORR duration, while both brain and rectal temperature at RORR were significantly positively correlated with BEC at RORR. The strength of the correlations and r2 values generated from linear regression analysis indicates that body temperature during intoxication can explain up to 52% of the variability in ethanol sensitivity in SS mice, but only 19% of the variability in ethanol sensitivity in LS mice. The correlational analyses are consistent with previous results based on comparisons between rectal temperature and ethanol sensitivity and extend to direct brain temperature measurement the evidence that decreasing temperature during intoxication decreases ethanol sensitivity in SS mice and increases ethanol sensitivity in LS mice.(ABSTRACT TRUNCATED AT 250 WORDS)