Ca(2+) and frequency dependence of exocytosis in isolated somata of magnocellular supraoptic neurones of the rat hypothalamus.
Ca(2+) and frequency dependence of exocytosis in isolated somata of magnocellular supraoptic neurones of the rat hypothalamus.
复制标题
大鼠下丘脑大细胞视上神经元分离体细胞胞吐作用的 Ca(2 ) 和频率依赖性。
DOI：
10.1113/jphysiol.2003.051136
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Moises,HylanC
中科院分区：
文献类型：
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作者：
Soldo,BrandiL;Giovannucci,DavidR;Stuenkel,EdwardL;Moises,HylanC
除了神经垂体神经末梢的动作电位诱发的胞吐释放外，神经激素精氨酸加压素（aVP）和催产素（OT）在下丘脑视上核和室旁核内经历Ca 2+依赖性体树突释放。然而，这种释放的细胞和分子机制尚未阐明。本研究采用全细胞膜片钳技术，结合高时间分辨的膜电容（Cm）测量和胞浆游离钙离子浓度（[Ca 2 +]i）的显微荧光测量，研究了大鼠视上核（SON）大细胞神经分泌细胞（MNCs）胞体胞吐的Ca 2+依赖性和刺激依赖性。诱发高压激活（HVA）钙电流（伊卡）和细胞内钙浓度升高的单个去极化步骤（≥20 ms）伴随着大多数（40/47）SON神经元的Cmin增加。Cm反应由初始的不依赖于Ca 2+的短暂成分和随后的由Ca 2+内流介导的持续增加的Cm（称为ΔCm）组成，并且随着去极化步长持续时间（20-200 ms）的相应延长而增加。根据这个关系，我们估计囊泡的释放速率为1533个囊泡s-1。神经元衍生动作电位波形（APW）作为刺激模板的传递诱发了ICa，也诱发了ΔCm，前提是APW以大于13 Hz的频率施加。在排乳反射期间记录的含OT神经元的爆发模式之后建模的一系列APW有效地支持了胞吐ΔCmin分离的MNC，表明SON神经元的胞体响应于具有Ca 2+依赖性胞吐活性的神经元活动的生理模式。
In addition to action potential‐evoked exocytotic release at neurohypophysial nerve terminals, the neurohormones arginine vasopressin (aVP) and oxytocin (OT) undergo Ca2+‐dependent somatodendritic release within the supraoptic and paraventricular hypothalamic nuclei. However, the cellular and molecular mechanisms that underlie this release have not been elucidated. In the present study, the whole‐cell patch‐clamp technique was utilized in combination with high‐time‐resolved measurements of membrane capacitance (Cm) and microfluorometric measurements of cytosolic free Ca2+concentration ([Ca2+]i) to examine the Ca2+and stimulus dependence of exocytosis in the somata of magnocellular neurosecretory cells (MNCs) isolated from rat supraoptic nucleus (SON). Single depolarizing steps (≥20 ms) that evoked high‐voltage‐activated (HVA) Ca2+currents (ICa) and elevations in intracellular Ca2+concentration were accompanied by an increase inCmin a majority (40/47) of SON neurones. TheCmresponses were composed of an initial Ca2+‐independent, transient component and a subsequent, sustained phase of increasedCm(termed ΔCm) mediated by an influx of Ca2+, and increased with corresponding prolongation of depolarizing step durations (20–200 ms). From this relationship we estimated the rate of vesicular release to be 1533 vesicles s−1. Delivery of neurone‐derived action potential waveforms (APWs) as stimulus templates elicitedICaand also induced a ΔCm, provided APWs were applied in trains of greater than 13 Hz. A train of APWs modelled after the bursting pattern recorded from an OT‐containing neurone during the milk ejection reflex was effective in supporting an exocytotic ΔCmin isolated MNCs, indicating that the somata of SON neurones respond to physiological patterns of neuronal activity with Ca2+‐dependent exocytotic activity.