Preweaning stimulation with urinary chemosignals and age of puberty in female mice.

Six experiments were conducted to assess the effects of preweaning stimulation with urinary chemosignals from four different sources on the age of sexual maturation in young female mice. The urinary chemosignals tested were those in male urine, urine from females in estrus, urine from pregnant or lactating females, and urine from females housed in groups. The split-litter technique was used for assigning mice to particular treatments. When treatments were applied during the period from 2 to 11 days postpartum, none of the chemosignals exerted any detectable influence on the age of first vaginal estrus. All 4 chemosignal treatments were effective in altering the age of puberty when treatment was applied daily from Days 12 to 21 postpartum. For urine from males and urine from estrous females, 3 days of treatment during the last 10 days prior to weaning at 21 days of age were sufficient to produce an acceleration of puberty. For urine from pregnant or lactating females, 5 days of treatment just prior to weaning were necessary to produce an acceleration of sexual development. For urine from grouped females, delays in puberty were produced only when the treatment lasted for 7 of the last 10 days prior to weaning. These findings suggest that the preweaning stimulus environment of young female mice may be important for their later sexual development. Further, use of the split-litter technique permitted the determination that variation in the age of puberty was smaller within than between litters; inheritance and/or maternal influences are clearly important factors affecting the age of sexual maturation.