BASIS FOR ANESTHETIC-INDUCED FATALITIES

这个项目的总体目标是确定的生理基础， 增强的兴奋性和对麻醉剂固有的异常反应， 恶性高热易感（MHS）人和猪的肌肉。第一章 首先，我们将测试从新生儿培养的肌管 MHS肌肉表现出MHS肌肉的特征性异常。 钙指示剂fura的荧光成像将用于 确定MHS肌管的肌浆钙是否异常 暴露于氟烷（引发MH发作）后升高。 的 MHS和正常肌管的强度-持续时间关系将被 使用全细胞膜片钳技术确定， MHS肌管收缩阈值低于正常。（二） MHS骨骼肌的兴奋-收缩（EC）偶联似乎 在横小管（TT）水平发生改变。 我们将测试 MHS肌管是否在TT水平上有功能缺陷， 记录与EC偶联相关的电压依赖性TT信号，即， 慢激活、长持续钙电流（I-s）和膜内钙电流 电荷运动 全细胞膜片钳技术将用于 表征I-s和电荷移动对电压的依赖性， 钙通道的激活、失活和敏感性 拮抗剂，以确定这些参数中的任何一个是否改变， MHS肌管。 丹曲洛林和阿珠莫林，EC偶联抑制剂， 预防MH发作，将进行研究，以确定它们是否改变I-S 和/或电荷移动。3)最后，我们将测试假设， 已知的MHS肌肉的肌浆网（SR）异常改变 在TT级别发挥作用。 肌肉杂合子的MH基因，这 SR钙通道的编码表现出一些相同的EC偶联 MHS肌肉的纯合子异常。 仔猪肌管培养 将使用MH基因的杂合性来确定 异常SR钙通道亚群的存在导致 改变了I-s和TT中的电荷运动。 SR对TT功能的影响 将通过记录整个细胞的I-s和电荷运动来进一步探索 正常肌管中的三种药物之一的存在下， SR钙通道：Ryanodine，结合SR钙通道， 使它们处于低电导状态，而氟烷或咖啡因， 其作用于SR钙通道以增强钙释放。 总之， 这些研究将探讨，除了有据可查的SR之外， 钙通道缺陷，也存在I-s和/或电荷异常 运动的MHS肌肉和是否异常SR钙通道可以 影响TT级别的事件。 EC偶联缺陷的阐明 在MHS肌肉将是重要的理解的基础， 开始新管理，并有助于澄清尚未确定的部分 骨骼肌的EC耦合过程。

The overall goal of this project is to define the physiological basis for enhanced excitability and abnormal responses to anesthetics inherent in muscles of malignant hyperthermia susceptible (MHS) humans and pigs. 1) First we will test the hypothesis that myotubes cultured from neonatal MHS muscles exhibit abnormalities characteristic of MHS muscles. Fluorescence imaging of the calcium indicator fura will be used to determine whether myoplasmic calcium of MHS myotubes is abnormally elevated after exposure to halothane (which triggers MH episodes). The strength-duration relationship of MHS and normal myotubes will be determined using whole cell patch-clamp techniques to establish that the contractile threshold of MHS myotubes is lower than normal. 2) Excitation-contraction (EC) coupling in MHS skeletal muscles appears to be altered at the level of the transverse-tubules (TT). We will test whether MHS myotubes are functionally defective at the TT level by recording voltage-dependent TT signals associated with EC coupling, i.e., the slow activating, long lasting calcium current (I-s) and intramembrane charge-movement. Whole cell patch-clamp techniques will be used to characterize I-s and charge-movement as to voltage-dependence of activation and inactivation and sensitivity to calcium channel antagonists to determine whether any of these parameters are altered in MHS myotubes. Dantrolene and azumolene, EC coupling inhibitors which prevent MH episodes, will be studied to determine whether they alter I-s and/or charge-movement. 3) Finally, we will test the hypothesis that the known sarcoplasmic reticulum (SR) abnormality of MHS muscles alters function at the TT level. Muscles heterozygous for the MH gene, which codes for the SR calcium channel exhibit some of the same EC-coupling abnormalities as homozygous MHS muscles. Myotubes cultured from piglets heterozygous for the MH gene will be used to determine whether the presence of a subpopulation of abnormal SR calcium channels results in altered I-s and charge movement in the TTs. SR influence on TT function will be further explored by recording whole cell I-s and charge-movement of normal myotubes in the presence of one of three drugs which act at the SR calcium channel: Ryanodine which binds to SR calcium channels and holds them in a low conductance state, and halothane or caffeine both of which act at the SR calcium channel to enhance calcium release. In sum, these studies will address whether, in addition to the well documented SR calcium channel defect, there is also an abnormality in I-s and/or charge movement in MHS muscles and whether abnormal SR calcium channels can influence events at the TT level. Elucidation of the EC coupling defect in MHS muscles will be of importance for understanding the basis for initiation of NM and contribute to clarifying an as yet undefined portion of the EC coupling process of skeletal muscles.