Motor and sensory innervation of muscle spindles in the neonatal rat.
Motor and sensory innervation of muscle spindles in the neonatal rat.
复制标题
新生大鼠肌梭的运动和感觉神经支配。
DOI：
10.1007/bf00304740
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Reichler,J
中科院分区：
文献类型：
--
作者：
Kucera,J;Walro,JM;Reichler,J
用电子显微镜连续跳跃横切面重建了4日龄大鼠比目鱼肌三种肌梭的神经和肌肉成分。每个纺锤体包含4个囊内梭纤维，包括至少一个袋1，一个袋2和一个链纤维。神经纤维由无髓运动和感觉轴突支配。初级和次级传入接近梭作为单一的轴突和梭内纤维的中央区域终止。单一配置文件的终端轴突占据的感觉神经肌肉接头的网站，类似于成人的感觉末梢。没有形态学特征表明从出生后4天的纺锤体的传入回缩。运动轴突接近纺锤体紧密包装在5-20个轴突的束中，并终止于袋和链纤维的近赤道和极区。每个梭内运动神经末梢的末端轴突的多个轮廓是可见的。更多的运动轴突支配出生后4天的纺锤体和更多的轴突终末可见在未成熟的梭内运动末梢比成人纺锤体。这些数据表明，出生后成熟的运动神经支配梭内纤维涉及消除多余的运动神经输入。在纺锤体运动系统发育过程中，突触的消失可能代表了一种机制，即单个γ轴突调节它们所支配的纺锤体数量。
Neural and muscular elements of three muscle spindles from the soleus muscles of 4-day-old rats were reconstructed by electron microscopy of skip-serial transverse ultrathin sections. Each spindle contained four encapsulated intrafusal fibers, including a minimum of one bag1, one bag2and one chain fiber. The fibers were innervated by unmyelinated motor and sensory axons. The primary and secondary afferents approached the spindles as single axons and terminated on the central region of the intrafusal fibers. Single profiles of terminal axons occupied the sites of sensory neuromuscular junctions, similar to adult sensory endings. No morphological features suggested retraction of afferents from 4-day postnatal spindles. Motor axons approached spindles tightly packed in bundles of 5–20 axons and terminated in the juxtaequatorial and polar regions of both bag and chain fibers. Multiple profiles of terminal axons were visible for each intrafusal motor ending. More motor axons innervated 4-day postnatal spindles and a greater number of axon terminals were visible in immature intrafusal motor endings than in adult spindles. The data suggest that postnatal maturation of motor innervation to intrafusal fibers involves the elimination of supernumerary motor nerve inputs. Synapse elimination in the development of the fusimotor system might represent a mechanism whereby individual γ axons adjust the number of spindles they innervate.