Analysis of the properties specific for sex hormone-dependent motoneurons

大鼠球海绵体脊髓核（SNB）支配会阴横面肌，包括球海绵体、提肛肌和肛门外括约肌。这些运动神经元是两性二态的，对雄性激素睾丸激素有反应。在雌性大鼠中，大多数SNB运动神经元在出生后早期死亡。在成年雄性大鼠中，SNB神经元的大小因阉割而减小，并因睾酮治疗而增加。本研究方案提出的主要问题有两个：第一，依赖性激素的SNB神经元的电生理特性与支配骨骼肌的运动神经元的电生理特性不同吗？;第二，睾酮对神经元大小的影响是直接作用于SNB运动神经元，还是由其靶会阴肌介导？采用膜片钳全细胞结构技术，记录了雄性和雌性大鼠SNB运动神经元的细胞内电位和膜电流。SNB运动神经元与支配脊肢肌肉的运动神经元的电生理特性仅在数量上有所不同。因此，性激素依赖性的SNB运动神经元和支配骨骼肌的运动神经元不能划分为两种不同的神经元类型。我们比较了阉割和睾酮对神经元大小的影响，分别是支配原始激素敏感的会阴肌的SNB运动神经元和支配缺乏雄激素敏感性的骨骼肌比目鱼肌的SNB运动神经元。阉割后，原会阴肌的SNB运动神经元的大小减小，睾酮操作后，SNB运动神经元的大小增加。相比之下，在阉割或睾酮治疗后，移植比目鱼肌的SNB运动神经元的大小保持不变。由此可见，激素对SNB运动神经元大小的调节是由其靶肌介导的。少

The spinal nucleus of the bulbocavernosus (SNB) in the rat innervates perineal striated muscles, including the bulbocavernosus, levator ani and external anal sphincter. These motoneurons are sexually dimorphic and responsive to the male hormone, testosterone. In female rats, the majority of SNB motoneurons die at early postnatal stages. In adult male rats, the size of SNB neurons is reduced by castration and increases by treatment with testosterone. The principal question posed in this research proposal is twofold : first, are the electrophysiological properties of the sex hormone-dependent SNB neurons are distinct from those of the motoneurons innervating skeletal muscles? ; second, is the effect of testosterone on neuronal size exerted directly on the SNB motoneurons or mediated by their target perineal muscles?Intracellular potentials and membrane currents were recorded from SNB motoneurons in male and female rats by the whole-cell configuration of patch-clamp techniques in thin sli … More ces of the lumbar spinal cord. The electrophysiological properties differed only quantitatively between the SNB motoneurons and the motoneurons innervating the hiridlimb muscles. It is concluded that the sex hormone-dependent SNB motoneurons and the motoneurons innervating the skeletal muscles cannot be classified into two distinct neuron types.The effects of castration and testosterone on neuronal size were compared between the SNB motoneurons reinnervating the original, hormone-sensitive perineal muscles and the SNB motoneurons reinnervating a skeletal muscle, the soleus muscle which lacks androgen sensitivity. The size of the SNB motoneurons reinnervating the original perineal muscles was reduced by castration and increased by testosterone manipulation. In contrast, the size of the SNB motoneurons reinnervating the grafted soleus muicle remained unchanged by castration or by treatment with testosterone. It is concluded that hormonal regulation of the size of SNB motoneurons is mediated by their target muscles. Less