Lømo T, Pockett S, Sommerschild H
Institute of Neurophysiology, University of Oslo, Norway.
Neuroscience. 1988 Feb;24(2):673-86. doi: 10.1016/0306-4522(88)90360-0.
Changes in the number and distribution of synaptic inputs and acetylcholine receptor clusters were studied during the formation of ectopic nerve-muscle junctions between the transplanted fibular nerve and the denervated soleus muscle of adult rats. The tibial nerve was cut 3 weeks after implanting the fibular nerve. New sites of transmission were first detected 3 days after the cut. These sites were located electrophysiologically, marked by dye and found to coincide with clusters of acetylcholine receptors. There were no ectopic clusters away from fibular nerve sprouts and no clusters on muscles which had not been denervated. Three days after cutting the tibial nerve, the acetylcholine receptor clusters, and probably also the sites of transmission, were randomly distributed along individual muscle fibres. Six days after the cut, the clusters continued to be randomly distributed whereas the synaptic inputs were either close together (within 300 microns) or more than 600 microns apart. Two weeks later the spatial distributions of both clusters and inputs were similar with peaks around 100-300 microns, 1200-1400 microns and 2000-2600 microns. No ectopic clusters were closer than 0.5 mm to the original endplate. We conclude that nerve-muscle contacts and associated acetylcholine receptor clusters initially form at random. One or a few of these contacts develop further and, as a result, the surrounding regions undergo changes that prevent the contacts initially formed there from being maintained. Apparently, in this preparation, approximately 1.5 mm length of fibre is needed to support the maturation and maintenance of each ectopic endplate (mean length 111 micron).
在成年大鼠移植的腓神经与失神经支配的比目鱼肌之间异位神经肌肉接头形成过程中，研究了突触输入和乙酰胆碱受体簇的数量及分布变化。植入腓神经3周后切断胫神经。切断后3天首次检测到新的传递位点。这些位点通过电生理定位，用染料标记，发现与乙酰胆碱受体簇重合。在远离腓神经芽的地方没有异位簇，在未失神经支配的肌肉上也没有簇。切断胫神经3天后，乙酰胆碱受体簇以及可能的传递位点沿单个肌纤维随机分布。切断后6天，簇继续随机分布，而突触输入要么靠得很近（在300微米内），要么相距超过600微米。两周后，簇和输入的空间分布相似，峰值出现在100 - 300微米、1200 - 1400微米和2000 - 2600微米左右。没有异位簇比原始终板更近于0.5毫米。我们得出结论，神经肌肉接触和相关的乙酰胆碱受体簇最初是随机形成的。其中一个或几个接触点进一步发育，结果，周围区域发生变化，阻止了最初在那里形成的接触点的维持。显然，在这种制备中，大约1.5毫米长的纤维需要用来支持每个异位终板（平均长度111微米）的成熟和维持。
