Zengel J E, Sosa M A, Poage R E
Department of Veterans Affairs Medical Center, Gainesville, FL.
Brain Res. 1993 May 14;611(1):25-30. doi: 10.1016/0006-8993(93)91772-k.
We have examined the effects of the peptide toxin omega-conotoxin GVIA (omega-CgTx), a known calcium channel blocker, on stimulation-induced changes in end-plate potential (EPP) amplitude at the frog neuromuscular junction. We found that the addition of this toxin in submicromolar concentrations reduced both the control EPP amplitude and the increase in EPP amplitude that normally occurs during repetitive stimulation under low quantal conditions. These effects of omega-CgTx developed slowly following its addition to the bathing solution, were concentration-dependent and were essentially irreversible. The effects of omega-CgTx appeared to result from reductions in the facilitation and augmentation components of stimulation-induced increases in release. While the effects of omega-CgTx on EPP amplitude could be reversed by increasing the extracellular concentration of Ca2+, we were unable to reverse the effects of the toxin on stimulation-induced increases in EPP amplitude. Thus it appears that omega-CgTx has a dual effect on neuromuscular transmission, perhaps by acting at two different presynaptic sites.
我们研究了已知的钙通道阻滞剂——肽毒素ω-芋螺毒素GVIA（ω-CgTx）对青蛙神经肌肉接头处刺激诱导的终板电位（EPP）振幅变化的影响。我们发现，添加亚微摩尔浓度的这种毒素会降低对照EPP振幅以及在低量子条件下重复刺激期间通常会出现的EPP振幅增加。ω-CgTx添加到浴液后，其这些作用发展缓慢，具有浓度依赖性，且基本不可逆。ω-CgTx的作用似乎是由于刺激诱导的释放增加中的易化和增强成分减少所致。虽然通过增加细胞外Ca2+浓度可以逆转ω-CgTx对EPP振幅的影响，但我们无法逆转毒素对刺激诱导的EPP振幅增加的影响。因此，ω-CgTx似乎对神经肌肉传递有双重作用，可能是通过作用于两个不同的突触前位点。
