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首页> 外文期刊>Canadian Journal of Physiology and Pharmacology >Sensing of extracellular calcium by neurones.
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Sensing of extracellular calcium by neurones.

机译：神经元对细胞外钙的感应。

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摘要

Transient changes in the intracellular concentration of Ca2+ provide a major signal for the regulation of many ion channels and enzymes in central neurones. In contrast, changes in extracellular Ca2+ are thought to play little or no signaling role. However, concentrations of extracellular calcium in the central nervous system do change dramatically during intense physiological and pathological stimulation, and recent studies have identified a number of membrane proteins that can sense and respond to changes in extracellular Ca2+. These include the recently cloned Ca(2+)-sensing receptor, hemi-gap-junction channels, and a potential Ca(2+)-sensing cation channel. Lowering extracellular Ca2+ strongly depolarizes and excites cultured hippocampal neurones. The excitation can be detected with decreases from physiological concentrations of as little as 100 microM. The depolarization results from activation of a nonselective cation current, which is sensitive to block by divalent and polyvalent cations. In outside-out patches, lowering Ca2+ induces a single-channel current with a conductance of 36 pS. Activation of this cation channel, in response to decreases in extracellular Ca2+, likely plays a key role in a positive feedback system of excessive neuronal depolarization, which accompanies intense excitatory activity in the hippocampus.
机译：细胞内Ca2 +浓度的瞬时变化为调节中枢神经元中的许多离子通道和酶提供了主要信号。相反，细胞外Ca 2+的变化被认为几乎没有或没有信号传导作用。然而，在强烈的生理和病理刺激下，中枢神经系统中细胞外钙的浓度确实发生了巨大变化，最近的研究已经发现了许多可以感知并响应细胞外Ca2 +变化的膜蛋白。这些包括最近克隆的Ca（2+）感应受体，半间隙连接通道和潜在的Ca（2+）感应阳离子通道。降低细胞外Ca2 +会强烈去极化并激发培养的海马神经元。可以从低至100 microM的生理浓度降低检测到激发。去极化是由于非选择性阳离子电流的激活而引起的，该电流对二价和多价阳离子的阻断敏感。在外而外的贴片中，降低Ca2 +会感应出单通道电流，电导值为36 pS。响应于细胞外Ca2 +的减少，该阳离子通道的激活可能在过度神经元去极化的正反馈系统中起着关键作用，神经系统去极化伴随着海马的强烈兴奋性活动。

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