Muramatsu Ken, Sasaki Sei-Ichi, Cho Yuichiro, Sato Kenji
Anatomy and Physiological Science, Department of Life Sciences and Bio-informatics, Tokyo Medical and Dental University, Tokyo, Japan.
Anat Sci Int. 2008 Dec;83(4):247-55. doi: 10.1111/j.1447-073X.2008.00238.x.
To investigate the spinal neural circuitry that controls the tonus of the external anal sphincter (EAS) in the cat, the size distribution of EAS motor fibers and their motoneurons (MN) was examined, and the presence of muscle spindles in EAS musculature was also tested for. The size distribution of EAS motor fibers was examined after degeneration of afferent fibers and that of their MN was measured, after labeling the cells with horseradish peroxidase. Both distributions were unimodal, thereby demonstrating the difficulty of distinguishing between alpha and potential gamma MN; but muscle spindles were not found in the musculature. Mechanisms underlying the spinally controlled tonus of the EAS remain unclear, including the nature and role of spinal reflexes. It is argued that non-spindle sensory receptors in the anal canal may provide the sensory component of a reflex circuit that contributes to this tonus.
为了研究猫中控制肛门外括约肌（EAS）张力的脊髓神经回路，我们检查了EAS运动纤维及其运动神经元（MN）的大小分布，并检测了EAS肌肉组织中肌梭的存在情况。在用辣根过氧化物酶标记细胞后，测量了传入纤维变性后EAS运动纤维的大小分布及其MN的大小分布。两种分布均为单峰分布，从而表明区分α运动神经元和潜在的γ运动神经元存在困难；但在肌肉组织中未发现肌梭。EAS脊髓控制张力的潜在机制仍不清楚，包括脊髓反射的性质和作用。有人认为，肛管中的非梭形感觉感受器可能为有助于这种张力的反射回路提供感觉成分。
