ION CHANNEL DISTRIBUTION AND MOBILITY

拟议的实验是针对长期目标， 了解神经元和其他可兴奋细胞如何调节复合物 电兴奋性和化学敏感性的模式， 表面。 因为离子通道负责细胞的电流 在很大程度上决定了它将如何接收，整合， 并传输信息，神经元必须能够合成类 适合其功能的离子通道，将它们输送到特定的 在表面上的位置，并删除它们时，他们的有用寿命 到期 拟议的实验解决了这些问题的几个方面 重要的细胞过程。 将使用骨骼肌纤维，因为 它们的表面可用于绘制离子通道分布， 大面积，因为它们执行几个常见的功能， 可兴奋细胞：它们接受突触输入，并启动和传播 动作电位 从本研究中获得的信息将与 涉及神经元兴奋性改变的神经系统疾病， 特别是神经肌肉传递障碍。 实验将使用青蛙和袜带的抽搐肌肉纤维 蛇和培养的鸡胚肌肉细胞。 焦电 记录，使用膜片钳技术将用于映射 细胞表面钠通道的空间分布， 特别强调突触接触的区域，在那里输入是 接收并启动动作电位。 的空间分辨率 测量值约为1 μ M，小到足以探索 Snake上终扣内和终扣间的通道分布 和青蛙纤维上的突触沟。 许多 设计实验来比较钠通道的组织 和乙酰胆碱受体，其位于连接区后的区域， 肌肉. 他们将确定膜是否分为 包含单独的离子通道群体的微观域，或 这两种类型的通道是否混合。 这些结果将 重要的是要了解通道是如何被限制在 连接后膜 其他实验将探索 的神经肌肉接头，以确定是否聚集 神经肌肉接头周围的这两种类型的通道通过 不同机制的相似性。 一些实验将测量钠通道迁移的能力 在流体膜内，决定通道的重要因素 分布 这些实验试图解决 两种技术之间的差异， 膜内钠通道的流动性。 最后，体内实验将首次测量 成人肌肉钠通道的更新率和寿命 动物

The proposed experiments are directed at the long-term goal of understanding how neurons and other excitable cells regulate the complex patterns of electrical excitability and chemical sensitivity on their surfaces. Because ion channels are responsible for a cell's electrical properties and to a large extent determine how it will receive, integrate, and transmit information, a neuron must be able to synthesize the classes of ion channels appropriate for its functions, deliver them to specific positions on the surface, and remove them when their useful lifetimes expire. The proposed experiments address several aspects of these important cellular processes. Skeletal muscle fibers will be used because their surfaces are accessible for mapping ion channel distributions over large areas, and because they perform several functions common to excitable cells: they receive synaptic input, and initiate and propagate action potentials. Information gained from this study will be relevant to neurological disorders that involve altered excitability of neurons and specifically to disorders of neuromuscular transmission. The experiments will use twitch muscle fibers from frogs and garter snakes, and cultured embryonic chick muscle cells. Focal electrical recordings, using a patch voltage clamp technique will be used to map the spatial distribution of sodium channels on the cellular surface, with particular emphasis on the region of synaptic contact, where inputs are received and action potentials are initiated. The spatial resolution of the measurements will be about 1 muM, small enough to explore the distribution of channels within and between terminal boutons on snake fibers and close to synaptic gutters on frog fibers. Many of the experiments are designed to compare the organization of sodium channels and acetylcholine receptors that populate the postjunctional region of the muscle. They will determine whether the membrane is divided into microscopic domains that contain separate populations of ion channels, or whether the two types of channels intermingle. These results will be important to understand how channels are confined within the postjunctional membrane. Other experiments will explore the development of the neuromuscular junction, to determine whether the aggregation of these two types of channels around the neuromuscular junction occurs by similar of different mechanisms. Some experiments will measure the ability of sodium channels to migrate within the fluid membrane, an important factor in determining the channel distribution. These experiments attempt to resolve the discrepancies between two techniques that have given very different pictures of the mobility of sodium channels within the membrane. Finally, in vivo experiments will make the first measurements of the turnover rate and lifetime of sodium channels in adult muscles in living animals.