Brazil O V, Fontana M D
Pflugers Arch. 1985 May;404(1):45-9. doi: 10.1007/BF00581489.
The effect produced by veratrine on transmembrane potential was investigated in five distinct regions of the isolated rat diaphragm blocked with either d-tubocurarine or alpha-bungarotoxin. It was found that small (0.4 micrograms/ml) and large (2.0 micrograms/ml) doses of veratrine depolarize only two or three of these regions. With the use of a very large (10.0 micrograms/ml) dose depolarization occurred in all five regions of the diaphragm but the effect was much larger in those areas of the muscle fibre membrane which were selectively depolarized by the smaller ones. These results clearly indicate either an unequal distribution of sodium channels activated by veratrine or differences in sodium channel density in distinct areas of the muscle fibre membrane. Supersensitivity of veratrinized muscles to potassium was confirmed. However, the sensitiveness to the depolarizing action of potassium was only increased in the regions of the diaphragm partially depolarized by veratrine. This suggests that partial depolarization of the muscle fibre membrane was actually the cause of the supersensitivity. The possible involvement of potassium and of the unequal depolarization of the muscle fibre membrane in the veratrine response is considered.
在分别用d -筒箭毒碱或α -银环蛇毒素阻断的离体大鼠膈肌的五个不同区域，研究了藜芦碱对跨膜电位的作用。结果发现，小剂量（0.4微克/毫升）和大剂量（2.0微克/毫升）的藜芦碱仅使其中两三个区域去极化。使用非常大的剂量（10.0微克/毫升）时，膈肌的所有五个区域均发生去极化，但在肌纤维膜中那些被较小剂量选择性去极化的区域，这种作用要大得多。这些结果清楚地表明，要么是藜芦碱激活的钠通道分布不均，要么是肌纤维膜不同区域的钠通道密度存在差异。证实了藜芦碱处理过的肌肉对钾超敏。然而，仅在藜芦碱使其部分去极化的膈肌区域，对钾去极化作用的敏感性才增加。这表明肌纤维膜的部分去极化实际上是超敏的原因。还考虑了钾以及肌纤维膜不均一去极化在藜芦碱反应中可能的作用。
