Schofield G G, Marshall I G
J Neurol Sci. 1980 Oct;48(1):21-34. doi: 10.1016/0022-510x(80)90147-1.
No major differences were observed in the mechanical properties of diaphragm, extensor digitorum longus and soleus muscles from athymic nude and control mice. Denervated soleus muscles from nudes and controls showed no significant differences in their sensitivities to the cholinoceptor agonists acetylcholine and carbachol, either in the absence or presence of the anticholinesterase, physostigmine, suggesting that postjunctional receptor function is essentially normal. Phrenic nerve-diaphragm preparations from nudes were less sensitive to the twitch-augmenting effects of neostigmine. No difference in the time course of endplate potentials (epps) between nudes and controls was seen either in the absence or presence of neostigmine. Hence the observed differences in twitch augmentation are unlikely to be due to differences in acetylcholinesterase activity in the two muscles. In normal mice miniature endplate potential (mepp) amplitude decreased and mepp frequency increased with age. These changes were associated with an increase in muscle fibre diameter and a concomitant decrease in membrane resistance. Such changes did not occur in nude mice; thus mepp amplitude remained, high as in young normal muscle. It is suggested that the thymus may play a role in muscle development and that the effects on neuromuscular transmission are secondary to changes in development. In cut diaphragm muscles transmitter reversal potentials in nudes and controls were not different. Although there was no difference in the amplitude of the first epp of a train, or in the immediately releasable acetylcholine store, the quantal content of the first epp, the probability of transmitter release, the total nerve terminal acetylcholine store and the transmitter mobilization rate were all reduced. It is considered probable that all the measurable differences in transmitter release can be explained in terms of the nude muscle fibre diameter being small and being associated with a small nerve terminal size.
在无胸腺裸鼠和对照小鼠的膈肌、趾长伸肌和比目鱼肌的力学性能方面未观察到显著差异。来自裸鼠和对照的失神经比目鱼肌对胆碱能受体激动剂乙酰胆碱和卡巴胆碱的敏感性在不存在或存在抗胆碱酯酶毒扁豆碱的情况下均无显著差异，这表明接头后受体功能基本正常。来自裸鼠的膈神经-膈肌标本对新斯的明的抽搐增强作用不太敏感。在不存在或存在新斯的明的情况下，裸鼠和对照之间的终板电位（epps）时间进程均未观察到差异。因此，观察到的抽搐增强差异不太可能是由于两块肌肉中乙酰胆碱酯酶活性的差异。在正常小鼠中，微小终板电位（mepp）幅度随年龄降低，mepp频率随年龄增加。这些变化与肌纤维直径增加以及膜电阻随之降低有关。这种变化在裸鼠中未发生；因此，mepp幅度保持在与年轻正常肌肉一样高的水平。提示胸腺可能在肌肉发育中起作用，并且对神经肌肉传递的影响是发育变化的继发结果。在切断的膈肌中，裸鼠和对照的递质反转电位没有差异。尽管一串刺激中第一个epp的幅度、即时可释放乙酰胆碱储备没有差异，但第一个epp的量子含量、递质释放概率、总神经末梢乙酰胆碱储备和递质动员率均降低。据认为，递质释放中所有可测量的差异很可能可以用裸鼠肌纤维直径小且与神经末梢尺寸小有关来解释。
