AGE AND STRAIN DIFFERENCES IN THE RATE OF DEVELOPMENT OF FUNCTIONAL TOLERANCE TO ETHANOL BY MICE

The time course of development of functional tolerance to ethanol was investigated in mice during the inhalation of ethanol vapor, using loss of righting reflex as the behavioral end-point. In male mice of the TO Swiss strain, weanling mice (18 days) showed no development of tolerance during continuous or repeated exposure to ethanol vapor for 6 h. Adolescent TO Swiss mice (35-40 days) showed rapid development of functional tolerance, reaching a state where 2 .times. the original effective concentration of ethanol in blood was required to produce loss of righting reflex within 5 h. Older adult mice (150-200 days) showed some development of tolerance during continuous or repeated exposure to ethanol for 5 h but this was much less than that seen in adolescent mice. When adolescent males of the C57BL, TO Swiss and DBA2 strains were compared, marked differences were observed. C57BL mice showed very rapid development of functional tolerance to ethanol in which more than 2 .times. the original effective dose was required to produce loss of righting reflex after about 3 h of ethanol exposure. TO Swiss mice showed somewhat slower development of ethanol tolerance. DBA2 mice showed little evidence of development of functional tolerance over the time course of these experiments. Similar age and strain differences may exist with respect to tolerance to the hypothermic effects of ethanol. Current concepts of ethanol sensitivity, tolerance and physical dependence were discussed.