A generational drift in rate of development of aversion to ethanol: associated shift in the sensitive period

In prior studies with CF1 mice obtained from a commercial source, the development of aversion to ethanol was accelerated by providing 5% sucrose (w/v) as only liquid source during age 4 to 8 weeks, but not when pretreatment was begun at age 12 weeks. In repeat studies the effect was not found consistently. The data suggested that this was due to changes in timing of the sensitive period associated with differences in the rate of development of aversion to ethanol. To keep breeding and rearing conditions as constant as possible, a mating colony was started with mice obtained from the commercial source. Successive generations of this line were studied. A spontaneous drift in the rate of development of aversion to ethanol, with increasing rates in successive generations, was observed. The sensitive period for the effect of 5% sucrose on this parameter was at age 8 to 12 weeks in the earlier more slowly developing generations; and gradually shifted to 0 to 4 weeks in later generations with a more rapid development of aversion to ethanol.