"In rats there is a sensitive period for the masculinization of soma size in motoneurons of the spinal nucleus of the bulbocavernosus (SNB), which extends beyond the sensitive period for masculinization of SNB cell number. The current study aimed to assess such sensitive periods in the SNB of mice. Female mice were exposed to testosterone propionate (TP) or vehicle during one of three potential sensitive periods of development; late embryonic (E 16-18), early postnatal (PN 1, 3, 5), or late postnatal (PN 7, 9, 11). Testosterone (T) was then provided to the females in adulthood via Silastic capsules to half of the animals in each group to serve as 'activational' background from which organizational effects of the perinatal hormones could be assessed. Early neonatal TP treatment significantly increased the adult number of SNB motoneurons in females, and also increased the size of both the somata and nuclei of the motoneurons in adulthood. As expected, adult T treatment also significantly increased the size of SNB somata and nuclei in all groups, but not the number of SNB cells. There was no significant interaction of perinatal and adult hormone treatment on cell number, soma size, or nuclear size. These results begin to define the sensitive periods in which androgens masculinize the SNB system in mice, where genetic tools are available to perturb mechanisms of androgen action on SNB development."--Page ii.
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