Analysis of Mechanisms for the Formation of Nerve Terminal Sprouts

神经末梢的发芽被认为是功能性突触传递中可塑性变化的形态学相关。为了验证这一假设，我们诱导发芽的运动神经末梢在大鼠伸趾长肌慢性传导阻滞的坐骨神经河豚毒素。在这些神经肌肉接头处释放的递质的量是根据终板电位的平均量子含量电生理学测量的。当神经传导被阻断6天后，约35%的后肢肌肉运动神经末梢出现出芽现象。通过电生理实验测量递质释放后，用荧光染料对每根肌纤维进行染色，并使用相同的神经肌肉接头进行形态学观察。坐骨神经传导阻滞6天后，所有神经肌肉接头的递质释放量均显著增加， ...更多信息 无论是否存在终端芽。有芽的连接处的总末端长度显著大于无芽的连接处。然而，有没有终端长度和发送器释放量之间的相关性。它的结论是，终端发芽和增加递质释放没有因果关系related.We以前已经表明，终端芽在神经肌肉接头的形成显着抑制治疗降钙素基因相关肽（CGRP）。这表明CGRP可能从神经元胞体转运到终末，在终末CGRP可能作为神经营养因子发挥作用。为了测试这种可能性，我们开发了一种高灵敏度的CGRP酶免疫测定法。通过该测定，发现坐骨神经中的CGRP含量为约100 pg/mm 2。此外，发现骨骼肌中检测到的约95%的CGRP来源于神经组织。在外周感觉和运动神经纤维中，发现CGRP以约1 mm/hr的速率沿离体方向运输。

Sprouting of nerve terminals has been assumed to be a morphological correlate of plastic changes in functional synaptic transmission. To test this assumption, we induced sprouting of motor nerve terminals in the rat extensor digitorum longus muscle by chronic conduction block of the sciatic nerve with tetrodotoxin. The amount of transmitter release at these neuromuscular junctions was measured electrophysiologically in terms of the mean quantum content of end-plate potentials., When the nerve conduction had been blocked for 6 days, about 35% of the motor nerve terminals examined in the hind leg muscle showed sprouting. After measurements of transmitter release by electrophysiological experiments, each muscle fiber was stained with fluorescent dye, and the same neuromuscular junctions were used for morphometric observations. Following a conduction block of the sciatic nerve for 6 days, all the neuromuscular junctions showed a significant increase in the amount of transmitter release uni … More formly, regardless of the presence or absence of terminal sprouts. The total terminal length in the junctions with sprouts was significantly greater than that in those without sprouts. However, there was no correlation between the terminal length and the amount of transmitter release. It is concluded that terminal sprouting and increased transmitter release are not causally related.We have previously shown that the formation of terminal sprouts at neuromuscular junctions is significantly inhibited by treatment with calcitonin gene-related peptide (CGRP). This suggests that CGRP may be transported from the neuron cell body to its terminal in which CGRP may act as a neurotrophic factor. To test this possibility, we developed a highly sensitive enzyme immunoassay for CGRP. With this assay, the CGRP content in the sciatic nerve was found to be about 100 pg/mm. Also, about 95% of CGRP detected in skeletal muscle was found to originate from neural tissues. In both the peripheral sensory and motor nerve fibers, CGRP was found to transport in the somatofugal direction at a rate of about 1 mm/hr. Less