Acceleration of puberty in female mice by a chemosignal from pregnant and lactating females: circadian rhythm effects.

Abstract

Two experiments were designed to test whether the urinary chemosignal excreted by pregnant and lactating female mice that accelerates puberty in young females is affected by circadian rhythms. The experiments also measured the possible influence of circadian rhythms on the response of the young recipient females. For urine from both pregnant and lactating females there was no difference in the effectiveness for accelerating puberty in urine collected during all 24 h. However, pregnancy urine used for treatment at 1800 and 0000 h, and lactation urine used for treatment at 1800, 0000 and 0600 h, all resulted in significantly earlier mean ages for puberty than pregnancy urine treatment at 0600 or 1200 h, or lactation urine treatment at 1200 h. There was also a significant interaction between the time of urine collection and the time of urine treatment for each urine source; urine was generally more effective in accelerating sexual development when used for treating young females at the same hour at which it had been collected, or at the time interval(s) just before or after the time at which it had been collected.