STIMULUS SECRETION COUPLING IN CAROTID BODY GLOMUS CELLS

呼吸和心血管系统的主要传感器， 缺氧是颈动脉体化学感受器， 以降低PaO 2或PHa。对这些刺激的敏感性是 出生时虚弱，出生后一两周内增加。缺氧和 酸度可能是由球细胞，分泌细胞， 并置到传入神经末梢。他们的作用至关重要， 化学转导，因为化学敏感性在分离后丧失， 神经末梢的血管球细胞最近的膜片钳记录 分离的血管球细胞显示出被缺氧抑制的K+电流。 这种抑制作用被假设在 缺氧的转导级联，导致去极化，钙内流 和增强的发射器释放。然而，我们的初步问题是， 这一机制的有效性，因为缺氧往往不能改变膜 电流的血管球细胞，在原位，和K+阻断剂，虽然 极大地影响细胞电流，可能不会阻断神经， 器官的分泌反应。 拟议的实验解决了两个基本问题， 转导过程首先，球细胞的特性是什么 分泌物和哪些是在缺氧时释放的？这一问题由 检查：i）Na+，K+和Ca+2通道在启动 （2）Ca ~（2+）i与血管球细胞分泌的关系 分泌和iii）核苷酸和磷酸化酶的调节作用 分泌活动。第二，在或 对分泌物的敏感性，以解释 血管球细胞刺激/分泌偶联？ 拟议的实验将采用一种新的和独特的化学感受器模型 它允许同时记录单纤维神经， 血管球的儿茶酚胺释放测量或膜片钳记录 cell.膜片钳数据用于评估囊泡融合事件 通过对膜电容的高分辨率监测。儿茶酚胺 使用碳纤维、Nafion涂层微电极测量分泌 结合扫描或安培伏安法。 这项工作的预期结果将使我们更好地了解 血管球细胞缺氧和酸性转导的机制及 对这些生理敏感性的成熟增加的基础 刺激。这可能会导致治疗策略，可以改变 从而改善呼吸暂停的治疗， 新生儿和老年受试者的通气不足。

The primary sensor of the respiratory and cardiovascular systems for hypoxia are the carotid body chemoreceptors which increase their activity in response to a decrease in PaO2 or PHa. Sensitivity to these stimuli are weak at birth and increase over the first week or two of life. Hypoxia and acidity are likely transduced by glomus cells, secretory cells in apposition to the afferent nerve endings. Their role is essential to chemotransduction because chemosensitivity is lost following separation of the glomus cell from the nerve endings. Recent patch clamp recordings of isolated glomus cells revealed a K+ current which is inhibited by hypoxia. This inhibition is hypothesized to play an essential role in the transduction cascade of hypoxia, leading to depolarization, calcium influx and enhanced transmitter release. However, our preliminary question the validity of this mechanism because hypoxia often fails to alter membrane currents of glomus cells, in situ, and K+ blocking agents, although greatly effecting the cellular currents, may not block the nerve or secretory response of the organ. The proposed experiments address two basic questions regarding the transduction process. Firstly, what is the identity of glomus cell secretogues and which are liberated during hypoxia? This is addressed by examining: i) the importance of Na+, K+ and Ca+2 channels in initiating glomus cells secretion, ii) the relationship between Ca+2i and cell secretion and iii) the modulatory role of nucleotides and phosphorylases on secretory activity. Secondly, what change occurs in the level of or sensitivity to secretogues to account for the developmental increase in glomus cell stimulus/secretion coupling? The proposed experiments will employ a new and unique chemoreceptor model which allows for simultaneous single-fiber nerve recordings and either measurement of catecholamine release or patch-clamp recording of glomus cell. Patch-clamp data is used for assessment of vesicular fusion events by high-resolution monitoring of membrane capacitance. Catecholamine secretion is measured using carbon-fiber, Nafion coated microelectrodes combined with scanning or amperometric voltammetry. The anticipated results from this work will allow us to better understand the mechanisms of glomus cell hypoxia and acidity transduction and the basis for the maturational increase in sensitivity to these physiologic stimuli. This may lead to therapeutic strategies that can alter chemosensitivity and thereby improve treatment of apnea and hypoventilation in the neonate and older subject.