Kurz E M, Bowers C A, Sengelaub D R
Program in Neural Science, Indiana University, Bloomington 47405.
J Comp Neurol. 1990 Feb 22;292(4):638-50. doi: 10.1002/cne.902920412.
Potential determinants of motoneuronal morphology were examined by using a sexually dimorphic, steroid-sensitive neuromuscular system in the rat spinal cord. In males, the spinal nucleus of the bulbocavernosus (SNB) innervates the perineal muscles bulbocavernosus (BC) and levator ani (LA), and the dorsolateral nucleus (DLN) innervates the ischiocavernosus muscle (IC). Adult females normally lack these motoneurons and the peripheral targets. Prenatal exposure of females to the androgen dihydrotestosterone propionate (DHTP) partially masculinizes this neuromuscular system and alters moto-neuron-to-muscle specificity, resulting in retained SNB target muscles anomalously innervated by motoneurons in the DLN. Because the morphology of SNB and DLN motoneurons normally differs significantly, the influence of spinal cord location and peripheral target on motoneuron morphology can be directly compared. Injection of cholera toxin conjugated to horseradish peroxidase (CTHRP) into the LA of DHTP-treated females labeled motoneurons predominantly in the SNB. These (SNB-LA) motoneurons in DHTP females were identical in all morphological measures to those of normal males. CTHRP injection into the BC of DHTP females labeled motoneurons in both the SNB and the DLN. SNB-BC motoneurons in DHTP females resembled those of normal males in process number and orientation, but were significantly smaller in dendritic length per motoneuron and in soma size. The DLN motoneurons anomalously projecting to the BC in DHTP females differed significantly from SNB-BC motoneurons in soma size and number and orientation of primary processes. However, these motoneurons were identical in all respects to DLN-IC motoneurons in DHTP females; DLN-IC motoneurons were similar to those of normal males in the orientation of their dendritic arbor, but were significantly smaller in dendritic length, soma size, and number of primary processes. These comparisons make it clear that DHTP selectively affects motoneuronal specificity and morphology in specific motoneuron classes. Further, motoneuronal morphology in the SNB/DLN system appears to be influenced more by spinal cord location than by peripheral target.
利用大鼠脊髓中一种具有性别差异、对类固醇敏感的神经肌肉系统，研究了运动神经元形态的潜在决定因素。在雄性大鼠中，球海绵体肌脊髓核（SNB）支配会阴肌球海绵体肌（BC）和肛提肌（LA），背外侧核（DLN）支配坐骨海绵体肌（IC）。成年雌性大鼠通常缺乏这些运动神经元及其外周靶标。雌性大鼠在产前暴露于雄激素丙酸二氢睾酮（DHTP）会使该神经肌肉系统部分男性化，并改变运动神经元与肌肉的特异性，导致保留的SNB靶肌肉被DLN中的运动神经元异常支配。由于SNB和DLN运动神经元的形态通常有显著差异，因此可以直接比较脊髓位置和外周靶标对运动神经元形态的影响。将与辣根过氧化物酶偶联的霍乱毒素（CTHRP）注入经DHTP处理的雌性大鼠的LA中，主要标记SNB中的运动神经元。这些DHTP处理的雌性大鼠中的（SNB-LA）运动神经元在所有形态学指标上与正常雄性大鼠的运动神经元相同。将CTHRP注入DHTP处理的雌性大鼠的BC中，标记了SNB和DLN中的运动神经元。DHTP处理的雌性大鼠中的SNB-BC运动神经元在突起数量和方向上与正常雄性大鼠的相似，但每个运动神经元的树突长度和胞体大小明显较小。在DHTP处理的雌性大鼠中，异常投射到BC的DLN运动神经元在胞体大小、初级突起数量和方向上与SNB-BC运动神经元有显著差异。然而，这些运动神经元在所有方面与DHTP处理的雌性大鼠中的DLN-IC运动神经元相同；DLN-IC运动神经元在树突分支方向上与正常雄性大鼠的相似，但在树突长度、胞体大小和初级突起数量上明显较小。这些比较清楚地表明，DHTP选择性地影响特定运动神经元类别的运动神经元特异性和形态。此外，SNB/DLN系统中的运动神经元形态似乎更多地受脊髓位置的影响，而不是外周靶标的影响。
