Breedlove S M
J Neurobiol. 1986 May;17(3):157-76. doi: 10.1002/neu.480170304.
The striated bulbocavernosus (BC) muscles of the rodent perineum are innervated by motoneurons in the spinal nucleus of the bulbocavernosus (SNB). In adulthood, the BC muscles are present in males only. However, newborn female rats have BC muscles, and SNB cells have made both anatomical and functional contact with them. Nevertheless, both motoneurons and muscles will degenerate unless androgens are administered perinatally. Such androgen treatment appears to be acting primarily on the BC muscles themselves, since the muscles are spared by androgen even after the loss of supraspinal neural afferents or even the entire lumbosacral spinal cord. Furthermore, androgen can spare SNB motoneurons that are themselves androgen insensitive. Perinatal steroid treatments can also alter the final spinal location of SNB cells as determined by retrograde tracing studies. Androgen continues to modify the morphology of the SNB system in adulthood, altering the size of both motoneurons and targets, which may be important for the reproductive function of BC muscles. Finally, the sexually dimorphic character of motoneuronal groups innervating perineal muscles seems to be common in mammals, since the homologue of the SNB, Onuf's nucleus, has more cells in males than in females in both dogs and humans.
啮齿动物会阴部的横纹球海绵体（BC）肌由球海绵体核（SNB）中的运动神经元支配。在成年期，BC肌仅存在于雄性体内。然而，新生雌性大鼠具有BC肌，且SNB细胞已与它们建立了解剖学和功能上的联系。尽管如此，除非在围产期给予雄激素，运动神经元和肌肉都会退化。这种雄激素治疗似乎主要作用于BC肌本身，因为即使在脊髓上神经传入纤维丧失甚至整个腰骶脊髓丧失后，肌肉仍能因雄激素而得以保留。此外，雄激素可以使本身对雄激素不敏感的SNB运动神经元得以保留。围产期类固醇治疗也可以改变通过逆行追踪研究确定的SNB细胞在脊髓中的最终位置。雄激素在成年期继续改变SNB系统的形态，改变运动神经元和靶标的大小，这可能对BC肌的生殖功能很重要。最后，支配会阴部肌肉的运动神经元群的性二态性特征在哺乳动物中似乎很常见，因为SNB的同源物奥努夫核在狗和人类中都是雄性比雌性有更多的细胞。
