Wilson D F, West A E, Lin Y
Department of Zoology, Miami University, Oxford, OH 45056, USA.
Neurosci Lett. 1995 Feb 15;186(1):29-32. doi: 10.1016/0304-3940(95)11274-z.
The effects of two nicotinic antagonists, d-tubocurarine (TC) and hexamethonium (HEX) were tested on the rat diaphragm neuromuscular junction during train-of-six stimuli to determine if a second action of these antagonists on evoked release could be demonstrated, in addition to its known impact of blocking the autoreceptor pathway. To minimize the autoreceptor pathway, the preparations were examined under low transmitter release conditions. It was observed that both compounds significantly depressed the end-plate potential amplitudes more than the miniature end-plate potential amplitudes, while also significantly depressing quantal release output. This inhibitory action is contrary to what is observed when transmitter release is high, where feedback regulation via the autoreceptors serves a prominent role. It is concluded that this depressive action on transmitter output contributes to onset of tetanic fade and that when higher concentrations of these antagonists are used this inhibitory action of TC and HEX may override autoreceptor feedback regulation.
在对大鼠膈神经肌肉接头进行串刺激期间，测试了两种烟碱拮抗剂——筒箭毒碱（TC）和六甲铵（HEX）的作用，以确定除了已知的阻断自身受体途径的影响外，这些拮抗剂对诱发释放的第二种作用是否能够得到证实。为了尽量减少自身受体途径的影响，在低递质释放条件下对标本进行检查。结果观察到，这两种化合物均使终板电位幅度比微小终板电位幅度更显著降低，同时也显著抑制量子释放输出。这种抑制作用与递质释放量高时所观察到的情况相反，在递质释放量高时，通过自身受体的反馈调节起主要作用。得出的结论是，这种对递质输出的抑制作用导致强直减退的发生，并且当使用更高浓度的这些拮抗剂时，TC和HEX的这种抑制作用可能会超过自身受体反馈调节。
