SODIUM REGULATION OF NEUROHORMONE SECRETION

拟议研究的长期目标是了解 钠调节神经激素/神经递质的机制(S) 在静息条件下和对刺激的反应中释放。这个 胞浆钠升高对神经递质易化的重要性 强直性刺激后的分泌物是公认的。当前 模型表明，钠的促进性作用源于 钙调节的改变。然而，最近，我们展示了 细胞内Na([Na]i)调节静息加压素的速率 钙离子作用下分离的神经垂体神经末梢(AVP)分泌 夹具条件。这导致了一种非常规的假设，即Na 它本身可以调节分泌，而且极有可能钠 可调节钙诱导(即刺激)的分泌。建议数 实验将利用大脑的神经末梢 下丘脑-神经-垂体系统，具有独特的解剖结构 允许分解分泌物的分子事件的优点 神经末梢的过程，需要比任何 其他神经末梢。具体目标是：1)利用时间分辨 全细胞膜片钳下的膜电容(Cm)测量 单个神经末梢决定钠的需要量 胞吐。细胞内[Na]将用荧光法测定 光谱学。这一方法将提供对 [NA]i关于胞吐的速度和程度并允许测定 胞吐释放部位所需的[Na]。2)使用离子 神经末梢和神经末梢种群的替代方案 放射免疫法测定AVP释放，我们将确定AVP释放的程度 NA对钙诱导的分泌有调节作用。3)使用完整的神经叶 准备我们将研究生理模式的影响 动作电位对[Na]i变化幅度和时程的影响。 然后，我们将在单个神经末梢上测量分泌活动 由使用厘米测量的类似变化引起的。我们将尝试 用荧光光谱定量测定内源缓冲容量 以及钠电流的测量。4)我们将尝试确定是否 NA诱导的AVP分泌利用独特的分泌机制或份额 其机制与钙诱导的分泌有共同之处。配基调控 受体相互作用或通过针对特定颗粒蛋白的抗体 钠诱导分泌的方式类似于钙诱导的分泌 将会被确定。监管的相似之处可能表明 机制。拟议中的实验对于描述正常的 神经末梢生理学，因为它们与学习、记忆和 神经系统疾病和对基础细胞学的理解 机械装置。

The long range goal of the proposed research is to understand the mechanism(s) of sodium regulation of neurohormone/neurotransmitter release under resting conditions and in response to stimulation. The importance of elevated cytosolic Na+ to facilitation of neurotransmitter secretion following tetanic stimulation is well established. Current models suggest that the facilitatory action of Na+ results from alteration of Ca2+ regulation. Recently, however, we showed that intracellular Na+ ([Na+]i) regulates the rate of resting vasopressin (AVP) secretion from isolated neurohypophysial nerve endings under Ca2+ clamp conditions. This has led to the unconventional hypothesis that Na+ itself can regulate secretion and to the remarkable possibility that Na+ may modulate Ca2+-induced (i.e. stimulated) secretion. The proposed experiments will utilize nerve endings of the hypothalamo-neurohypophysial system, which posses unique anatomical advantages allowing resolution of the molecular events of the secretory process in nerve endings, to be studied in greater detail than in any other nerve endings. The specific aims are: 1) to utilize time-resolved membrane capacitance (Cm) measurements, under whole cell patch clamp on individual nerve endings to determine the Na+ requirements for exocytosis. Intracellular [Na+] will be measured by fluorescence spectroscopy. This approach will provide a quantitative evaluation of [Na+]i on the rate and extent of exocytosis and allow determination of the [Na+]i required at an exocytotic release site. 2) Using ionic substitution protocols on populations of nerve endings and radioimmunoassay for AVP release, we will determine the extent to which Na+ modulates Ca2+-induced secretion. 3) Using the intact neural lobe preparation we will investigate the effect of physiologic patterning of action potentials on the amplitude and time course of changes in [Na+]i. We will then measure, on single nerve endings, the secretory activity induced by similar changes using Cm measurements. We will attempt to quantitate the endogenous buffer capacity using fluorescence spectroscopy and measurements of Na+ currents. 4) We will attempt to determine if Na+-induced AVP secretion utilizes unique secretory mechanisms or shares mechanisms in common with Ca2+-induced secretion. Regulation by ligand receptor interactions or by antibodies against specific granule proteins of Na+-induced secretion in a manner similar to Ca2+ induced secretion will be determined. Similarity of regulation may suggest commonality of mechanism. The proposed experiments are crucial to describe the normal physiology of nerve endings both as they relate to learning, memory and disease of the nervous system and in understanding basic cellular mechanisms.