ION CHANNELS, ACTION POTENTIALS, AND QUANTAL SECRETION

大电导Ca 2+和电压依赖性K+通道（称为BK 通道）是普遍分布的离子通道， 膜下Ca ~（2+）对细胞电兴奋性的调节。 BK通道激活与Ca 2+内流的这种偶联起到了负作用。 反馈作用终止动作电位过程中的Ca 2+内流。 这 对于诸如发射机端接 突触释放，调节神经内分泌激素分泌 细胞，以及耳蜗毛细胞的频率调谐。 这 该提案旨在定义BK通道的关键属性， 生理作用。 此外，该提案将评估 假设BK通道可能在调节 电兴奋性和分泌，部分是因为选择性的 与特定的Ca 2+通道亚型相关。 解决这些 问题，膜片钳记录方法，共聚焦成像， 电化学定位离子通道和碳纤维电极 (CFE)大鼠个体的量子分泌信号记录 将使用肾上腺嗜铬细胞。 该提案以一个 BK通道激活如何可能严重依赖于 选择性偶联到特定的Ca 2+通道。 然后，它继续进行到 BK通道所起的生理作用以及 BK通道与Ca ~（2+）通道的偶联可能具有调节作用 细胞的兴奋性和分泌。 在此提出的原则 不仅对神经内分泌细胞有重要意义， 对于所有BK通道激活依赖于 高浓度的Ca 2+仅在开放Ca 2+附近发现 渠道 BK通道定位功能异常将影响 对正常的可兴奋细胞功能有很大影响。 因此，理解 BK通道在调节递质释放和 在调节神经元兴奋性是一个关键因素， 能够识别与以下因素相关的关键变化： 突触传递、分泌或兴奋性的病理。

Large conductance Ca2+ -and voltage-dependent K+ channels (termed BK channels) are ubiquitously distributed ion channels that couple changes in submembrane Ca2+ to regulation of cellular electrical excitability. This coupling of BK channel activation to Ca2+ influx plays a negative feedback role to terminate Ca2+ influx during action potentials. This is critical to processes as diverse as the termination of transmitter release at synapses, regulation of hormone secretion from neuroendocrine cells, and the frequency tuning of hair cells in the cochlea. This proposal seeks to define the key properties of BK channels underlying their physiological roles. Furthermore, the proposal will evaluate the hypotheses that the BK channel may play a key role in the regulation of electrical excitability and secretion, in part, because of a selective association with particular subtypes of Ca2+ channels. To address these issues, patch-clamp recording methodologies, confocal imaging of immunohistochemically localized ion channels, and carbon fiber electrode (CFE) recordings of quantal secretory signals from individual rat adrenal chromaffin cells will be utilized. The proposal begins with an examination of how BK channel activation may be critically dependent on selective coupling to particular Ca2+ channels. It then proceeds to the physiological roles played by BK channels and the implications that coupling of BK channels to Ca2+ channels may have both for regulation of cellular excitability and secretion. The principles developed here are likely to be of significance not only for neuroendocrine cells, but for all excitable cells where BK channel activation is dependent on the high concentrations of Ca2+ only found in the vicinity of open Ca2+ channels. Abnormal function on localization of BK channels will impact significantly on normal excitable cell function. Thus, understanding the role of BK channels both in regulation of transmitter release and in regulation of neuronal excitability is a critical element in being able to identify the key alterations that occur in association with pathologies of synaptic transmission, secretion, or excitability.