Womble M D
Am J Anat. 1986 Jun;176(2):191-205. doi: 10.1002/aja.1001760208.
The present investigation was undertaken to study the relationship between acetylcholine receptor (AchR) clustering and endplate formation within regenerating skeletal muscle grafts. Silver staining of nerves was combined with rhodamine-alpha-bungarotoxin labeling of AchR clusters in heterotopic grafts of the rat soleus muscle. Two major graft procedures were used: whole muscle grafts and grafts which lacked the zone of original motor endplates (MEP-less grafts). These categories were subdivided into standard grafts, where subsequent innervation was allowed, and noninnervated grafts, which were experimentally deprived of innervation. Grafting brought about the death and removal of muscle fibers, followed by regeneration of myotubes within surviving basal lamina sheaths. A transient population of small extra-junctional AchR clusters spontaneously appears shortly after myotube formation in all four muscle graft types. Early myotubes of whole muscle grafts (both innervated and standard grafts, prior to the time of innervation) also develop presumptive secondary synaptic clefts and large, organized aggregations of AchRs at original synaptic sites. At later times, nerves regenerating into standard whole muscle and MEP-less grafts lead to the formation of numerous ectopic endplates. In whole muscle grafts, endplates may also form at original synaptic sites. Functional graft innervation is achieved in whole muscle and MEP-less grafts as early as 20 days postgrafting. The results of this study support the existence of still-unknown factors associated with the original synaptic site which can direct postsynaptic differentiation independent of innervation. They also demonstrate that functional endplates may form in mammalian muscle grafts at both original synaptic sites and ectopic locations, thus indicating that the zone of original synaptic sites is not necessary for the establishment of numerous functional and morphologically well-differentiated endplates.
本研究旨在探讨再生骨骼肌移植物中乙酰胆碱受体（AchR）聚集与终板形成之间的关系。将神经银染与用罗丹明-α-银环蛇毒素标记大鼠比目鱼肌异位移植物中的AchR簇相结合。采用了两种主要的移植方法：全肌移植和缺乏原始运动终板区域的移植物（无运动终板移植物）。这些类别又细分为标准移植物（允许后续神经支配）和去神经支配移植物（通过实验剥夺神经支配）。移植导致肌纤维死亡和清除，随后在存活的基膜鞘内肌管再生。在所有四种肌肉移植物类型中，肌管形成后不久会自发出现短暂的小的接头外AchR簇群体。全肌移植物的早期肌管（包括有神经支配的和标准移植物，在神经支配之前）在原始突触部位也会形成假定的次级突触间隙和大的、有组织的AchR聚集。在后期，再生进入标准全肌和无运动终板移植物的神经会导致形成许多异位终板。在全肌移植物中，终板也可能在原始突触部位形成。早在移植后20天，全肌和无运动终板移植物就能实现功能性神经支配。本研究结果支持存在与原始突触部位相关的未知因素，这些因素可以独立于神经支配直接引导突触后分化。它们还表明，功能性终板可能在哺乳动物肌肉移植物的原始突触部位和异位位置形成，从而表明原始突触部位区域对于建立许多功能和形态上分化良好的终板并非必要。
