Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, Ohio, USA.
J Neurophysiol. 2010 Nov;104(5):2352-8. doi: 10.1152/jn.00460.2010. Epub 2010 Aug 25.
Block of neurotransmission at the mammalian neuromuscular junction triggers an increase in the number of vesicles released (quantal content). The increase occurs whether nerve and muscle activity are both blocked by placement of a tetrodotoxin (TTX) containing cuff on the nerve or whether muscle activity is selectively blocked by injection of α-bungarotoxin (BTX). We used ANOVA to examine whether the mechanism underlying the increase in quantal content differed between the two types of activity blockade. We found that TTX-induced blockade increased the probability of release (p), whereas BTX-induced blockade increased the number of releasable vesicles (n). The lack of increase in p when postsynaptic activity was blocked with BTX suggests that block of presynaptic activity triggers the increase. To determine whether n is regulated by mismatch of pre- and postsynaptic activity introduced by BTX injection we combined BTX and TTX and still found an increase in n. We conclude that block of acetylcholine binding to acetylcholine receptors during spontaneous release triggers the increase in n.
在哺乳动物神经肌肉接头处阻断神经递质传递会触发释放的囊泡数量增加（量子含量）。这种增加发生在神经和肌肉活动都被放置在神经上的含有河豚毒素 (TTX) 的袖带阻断，或者肌肉活动被注射α-银环蛇毒素 (BTX) 选择性阻断的情况下。我们使用方差分析来检查两种活动阻断下量子含量增加的机制是否不同。我们发现，TTX 诱导的阻断增加了释放的概率 (p)，而 BTX 诱导的阻断增加了可释放的囊泡数量 (n)。当用 BTX 阻断突触后活动时，p 没有增加，这表明是突触前活动的阻断引发了增加。为了确定 n 是否受到 BTX 注射引起的前后突触活动不匹配的调节，我们结合了 BTX 和 TTX，仍然发现 n 增加。我们得出结论，在自发释放期间阻断乙酰胆碱与乙酰胆碱受体的结合会触发 n 的增加。
