钾通道阻断剂4-氨基吡啶诱导海马CA1锥体神经元钙瞬变

Calcium transient of CA1 pyramidal neurons induced by potassium blocker 4-aminopyridine in acute hippocampal slices

目的 研究4-氨基吡啶（4-AP）诱导的急性脑片海马CA1锥体神经元钙瞬变现象,探讨钾通道功能与钙瞬变的关系及可能机制.方法 荧光探针标记正常大鼠急性脑片海马神经元.共聚焦显微镜技术进行钙成像,观察不同浓度4-AP及细胞灌流液条件对神经元钙瞬变的影响.结果 低浓度（〈15 mmol/L）4-AP诱导的钙瞬变峰值与剂量呈线性相关（r2=0.910,P=0.000）,高浓度（20～80 mmol/L）4-AP诱导的钙瞬变峰值随浓度增高而下降.在无钙灌流液条件下,4-AP诱导的钙瞬变峰值水平下降,达峰时间延长,与含钙灌流液比较差异有统计学意义（P〈0.05）.结论 4-AP可诱导急性脑片海马CA1锥体神经元的钙瞬变,其机制包括细胞外钙内流与钙库钙释放.

Objective To investigate the calcium transient of CA1 pyramidal neurons induced by potassium blocker 4-aminopyridine （4-AP） in acute hippocampal slices to explore the relation between potassium channel function and calcium transient, and their mechanism. Methods Fluorescent probe was employed to mark the hippocampai neurons in acute brain slices of rats; confocal microscopy was used to perform calcium imaging to observe the influences of different concentrations of 4-AP and perfusate with/without calcium on calcium transient of CA1 pyramidal neurons. Results The response of [Ca2＋]I to lower concentration of 4-AP （〈15 mmol/L） was in a dose-dependent manner （r2=0.910, P=0.000）; the higher the concentration of 4-AP （20-80 mmol/L）, the lower the peak level of calcium transient. The latency and amplitude of calcium transient induced by 4-AP were obviously reduced when the extracellular condition was switched to an absence of calcium, which was significantly different as compared with that with calcium （P〈0.05）. Conclusion Blockade of potassium channels with 4-AP can increase [Ca2＋]I in the hippocampal pyramidal neurons of acute slices. The increase of [Ca2＋]1 to 4-AP could be ascribe to calcium release from intracellular stores and calcium influx from extracellular matrix.