Wines M M, Hall-Craggs E C
J Comp Neurol. 1986 Jul 8;249(2):152-6. doi: 10.1002/cne.902490203.
The cranial belly of the anterior gracilis muscle of the rat has two discrete motor endplate zones. A proximal zone is innervated by short branches of the obturator nerve, and a distal zone is innervated by (usually) two longer branches. Each muscle fiber is innervated at a single motor endplate although a substantial number lie within both endplate zones. In addition, motor units are divided between the two zones. In order to dissociate the role of the denervated endplate from that of the denervated muscle fiber in the promotion of motoneuron sprouting, the distal endplate zone in this model was denervated and the response at the proximal zone was studied. Comparisons were made with partial denervation of the muscle by division of the L4 ventral ramus and with partial denervation of the distal endplate zone. Denervation of the distal endplate zone produced profuse terminal sprouting at the proximal zone whereas division of L4 predominantly produced nodal sprouting at both zones. Partial denervation of the distal zone resulted in nodal sprouts in that zone and again mainly terminal sprouts at the proximal zone. The repeated association of terminal sprouting with division of the motor axons supplying the distal zone together with the knowledge that motor units are distributed between the two zones led to the conclusion that the terminal sprouting was stimulated by the reduction in size of motor units rather than by the presence of denervated muscle fibers in the vicinity of the endplates.
大鼠前股薄肌的颅侧肌腹有两个离散的运动终板区。近端区由闭孔神经的短支支配，远端区（通常）由两支较长的分支支配。尽管有相当数量的肌纤维位于两个终板区内，但每根肌纤维仅在一个运动终板处接受神经支配。此外，运动单位在这两个区域之间分布。为了区分失神经终板和失神经肌纤维在促进运动神经元发芽中的作用，在该模型中对远端终板区进行失神经处理，并研究近端区的反应。将其与通过切断L4腹侧支对肌肉进行部分失神经处理以及对远端终板区进行部分失神经处理的情况进行比较。远端终板区失神经处理导致近端区出现大量终末发芽，而切断L4主要在两个区域产生结状发芽。远端区部分失神经处理导致该区域出现结状芽，近端区再次主要出现终末芽。终末发芽与供应远端区的运动轴突切断反复相关，再加上运动单位在两个区域之间分布这一事实，得出的结论是，终末发芽是由运动单位大小的减小而非终板附近失神经肌纤维的存在所刺激的。
