Some effects of mouse urine on neonatal growth and reproduction.

An experiment is described in which urine collected from female mice at different stages of the reproductive cycle and from adult male mice was applied to the nasal region of neonatal female mice. The topical application of pseudopregnant urine had an accelerating effect on growth while the application of urine from virgin female donors and mice in late pregnancy was associated with a slow rate of growth. Male urine accelerated the sexual maturation of the mice while the application of urine from virgin females delayed vaginal introitus and first oestrus. The application of both male and pseudopregnant urine was associated with a high incidence of pregnancy when adult. It is suggested that the urine of adult mice contains an active substance(s) which can affect the growth of young female mice and that the effect is dependent on the reproductive state of the donor. The block to pregnancy that occurs when a recently mated mouse is exposed to an unfamiliar adult male (Bruce 1959, 1960) can be effected by applying urine from an unfamiliar adult male direct to the external nares of the pregnant female, thus, demonstrating that the pheromone responsible for the block is present in bladder-urine (Dominic 1964). Synchronization of oestrus occurs when mice that have been housed in all-female communities are mated or exposed to the presence of a male. This can also be initiated by applying male urine directly to the nasal region (Marsden & Bronson 1964). The presence of the male and the topical application of the urine shorten the oestrous cycle (Whitten effect). Exposure of neonatal female mice to the presence of adult males accelerates sexual development (Castro 1967; Vandenbergh 1967) and the pheromone responsible has been shown to be airborne (Vandenbergh 1969). The presence of adult male and female mice was also observed to exercise a differentiating effect on the growth and behaviour in an open field test of young mice (Fullerton & Cowley 1971). The present study was aimed at ascertaining whether, as in the Bruce effect and Whitten effect, the active substance responsible for the growth changes was contained in the urine and whether the urine of mice at different stages of pregnancy and pseudopregnancy would affect the sexual and somatic development of young mice if topically applied to the external nares. Methods Urine collected from albino mice of the CS1 strain was applied to the external surface of the nose of …