SODIUM CHANNEL GATING IN MODELS OF MYOTONIA

本研究的目的是：1）研究钠通道 灭活大鼠骨骼肌，和2）研究大鼠 人肌肉肌强直性疾病的模型，其中膜 兴奋性可能受损。 关于钠通道的两种假说 将测试门控。 首先，钠电流增加 通过在大鼠骨骼肌中产生肌强直的治疗。 第二，钠电流密度的增加是由于 电压依赖性钠通道失活的改变。 的 所采用的技术是：1）松散膜片电压钳将被 用于测量钠电流，和2）单纤维类型 纤维将通过组织化学染色和钠 十二烷基硫酸盐聚丙烯酰胺凝胶电泳（SDS-PAGE）。 实验测量对照组和肌强直组的钠电流 使用本实验室开发的技术， 几个小时的稳定电流记录。 中的肌强直 大鼠肌肉将通过以下方式产生：1）将纤维浸泡在氯化物中， 缺乏溶液，2）用芳族羧酸处理纤维， 酸以降低氯离子传导性，和3）用20， 25-二氮胆固醇 钠通道快的电压依赖性 将研究缓慢失活以检查是否发生变化 钠电流密度的变化可归因于快 或缓慢失活。 这些项目将提供1）关于兴奋性的新信息 哺乳动物骨骼肌;和2）可能的新信息， 不同形式肌强直的病理生理学。

The objectives of this proposal are: 1) to study sodium channel inactivation in rat skeletal muscle, and 2) to investigate rat model of human muscle myotonic disorders in which membrane excitability may be impaired. Two hypotheses about sodium channel gating will be tested. First, that sodium currents are increased by treatments which produce myotonia in rat skeletal muscle. Second, that the increase in sodium current density is due to an alteration in voltage-dependent sodium channel inactivation. The techniques employed are: 1) the loose-patch voltage clamp will be used to measure sodium currents, and 2) the fiber type of single fibers will be determined by histochemical staining and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The experiments measure sodium currents in control and myotonic muscle using techniques developed in this laboratory that permit stable current recordings of cells for several hours. Myotonia in rat muscle will be produced by: 1) bathing a fiber in a chloride- deficient solution, 2) treating fibers with aromatic carboxylic acids to reduce chloride conductance, and 3) treating rats with 20, 25-diazacholesterol. The voltage dependence of sodium channel fast and slow inactivation will be studied to examine whether changes in sodium current density can be attributed to alterations in fast or slow inactivation. These projects will provide 1) new information on the excitability of mammalian skeletal muscle; and 2) possibly new information on the pathophysiology of different forms of myotonia.