Breedlove S M, Arnold A P
Science. 1980 Oct 31;210(4469):564-6. doi: 10.1126/science.7423210.
The fifth and sixth lumbar segments of the rat spinal cord were found to contain a sexually dimorphic nucleus, the spinal nucleus of the bulbocavernosus (SNB). The SNB, which contains motoneurons innervating perineal striated muscles in normal male rats, is adiminished or absent in normal females and in males with a genetic mutation rendering them insensitive to androgens. The presence of the nucleus is apparently not dependent on genetic sex, but on the action of androgens. The motoneurons of the adult male SNGH accumulate hormone after systemic injections of radioactive testosterone or dihydrotestosterone, but not estradiol, and the SNB motoneurons accumulate more of the injected androgens than do other motoneurons in the same spinal segments. These results demonstrate a morphological sex difference in hormone-sensitive motoneurons that are probably involved in the sexually dimorphic copulatory behavior of the rat.
研究发现，大鼠脊髓的第五和第六腰段含有一个性二态核团，即球海绵体肌脊髓核（SNB）。在正常雄性大鼠中，SNB包含支配会阴横纹肌的运动神经元，而在正常雌性大鼠以及因基因突变而对雄激素不敏感的雄性大鼠中，该核团则缩小或缺失。该核团的存在显然不取决于遗传性别，而是取决于雄激素的作用。成年雄性SNB的运动神经元在全身注射放射性睾酮或双氢睾酮后会积累激素，但注射雌二醇后则不会，并且与同一脊髓节段的其他运动神经元相比，SNB运动神经元积累的注射雄激素更多。这些结果表明，激素敏感的运动神经元存在形态学上的性别差异，这可能与大鼠的性二态交配行为有关。
