P物质阳性神经纤维对球海绵体肌和坐骨海绵体肌运动神经元的支配——HRP逆行示踪与免疫细胞化学研究

SUBSTANCE P POSITIVE FIBER INNERVATION ON MOTONEURONS INNERVATING BURBOSPONGIOSUS AND ISHIOCAVERNOSUS MUSCLESHRP RETROGRADE TRACING AND IMMUNOCYTOCHEMICAL STUDY

本研究应用 HRP逆行示踪与免疫细胞化学相结合的双重反应技术观察了 P物质纤维与前角躯体运动神经元的关系。用 WGA-HRP经大鼠球海绵体肌和坐骨海绵体肌注射后 ,逆行示踪标记的运动神经元分布于 L5 和 L6脊髓前角的背内侧核和背外侧核内侧部。 SP能纤维广泛分布于脊髓灰质 ,其中以后角最为密集。光镜下可见在前角的背内侧核和背外侧核内 ,SP阳性纤维呈点状和带有钮扣状膨大的纤维分布于逆行标记的运动神经元周围。电镜下可见 SP阳性纤维终末含有少量的大型囊泡和多量的清亮小泡。常见 SP阳性纤维末梢与 HRP逆行标记的运动神经元有紧密联系 ,并证明二者形成突触结构。本研究首次证实脑下行 P物质阳性纤维对调控球海绵体肌和坐骨海绵体肌运动神经元有直接支配关系 ,提示

Penile erection is due to activation of proerectile neurons located in the sacral parasympathetic nucleus of the L 5～S 1 spinal cord in the rat. Contraction of the bulbospongiosus and ischiocavernosus striated muscles reinforces penile erection and participates in ejaculation. Motoneurons innervating bulbospongiosus and ischiocavernosus striated muscles are located in Onuf's nucleus in the ventral horn of the L 5～L 6 spinal cord. Little is known about innervation of substance P on Onuf's nucleus. Double labeling technique including immunocytochemistry of substance P and retrograde HRP transport tracing was performed. Motoneurons were labeled by wheat germ agglutinin-horseradish peroxidase injected in the bulbospongiosus and the ischiocavernosus striated muscles. Retrograde labeled motoneurons were located in the dorsomedial and in the medial part of dorsolateral nuclei. Fibers immunoreactive for substance P were largely and densely distributed in the dorsal horn, the dorsal grey commissure, the intermediolateral column and the ventral horn. Some substance P fibers occurred in close apposition with retrograde labeled motoneurons, and synapses were demonstrated at the ultrastructural level. This study for the first time provides morphological support for innervation of substance P fiber on motoneurons innervating the bulbospongiosus and the ischiocavernosus muscles participating in erection and ejaculation.