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首页> 外文期刊>Journal of Neurophysiology >Concentration dependence of bicarbonate-induced calcium current modulation.
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Concentration dependence of bicarbonate-induced calcium current modulation.

机译：碳酸氢盐引起的钙电流调节的浓度依赖性。

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摘要

High-voltage-activated calcium currents (HVA) of CA1 neurons are prominently attenuated following a switch from HEPES-buffered solution to one buffered with CO(2)/HCO(3)(-). In the present study we investigated whether bicarbonate ions or the dissolved CO(2) induce this alteration in current characteristic. The study was carried out on freshly isolated CA1 neurons using the whole cell patch-clamp technique. Maximal calcium conductance and the mean peak amplitude of the currents showed a concentration-dependent decrease when cells were consecutively bathed in solutions containing increasing amounts of bicarbonate and CO(2). This decrease is best described by the Hill equation, yielding a maximal attenuation of 69%, a half-maximal concentration (EC(50)) of 7.4 mM HCO(3-), and a Hill coefficient of 1.8. In parallel, the potentials of half-maximal activation (V(h,a)) and inactivation (V(h,i)) were linearly shifted in hyperpolarizing direction with a maximal shift, in the 10% CO(2)/37 mM HCO(3)(-) containing solution of 10 +/- 1 mV for V(h,a) (n = 23) and 17 +/- 1.4 mV for V(h,i) (n = 18). When currents were evoked in solutions containing equal concentrations of bicarbonate but different amounts of CO(2), only nonsignificant changes were observed, while marked alterations of the currents were induced when bicarbonate was changed and CO(2) held stable. The experiments suggest that bicarbonate is the modulating agent and not CO(2). This bicarbonate-induced modulation may be of critical relevance for the excitation level of the CNS under pathological situation with altered concentration of this ion, such as hyperventilation and metabolic acidosis.
机译：从HEPES缓冲溶液切换到一个用CO（2）/ HCO（3）（-）缓冲的溶液切换后，CA1神经元的高压激活钙电流（HVA）显着衰减。在本研究中，我们调查了碳酸氢根离子或溶解的CO（2）是否引起电流特征的这种改变。该研究使用全细胞膜片钳技术在新鲜分离的CA1神经元上进行。当细胞连续沐浴在含有增加量的碳酸氢盐和CO（2）的溶液中时，最大的钙电导率和电流的平均峰值幅度显示出浓度依赖性的降低。这种下降最好用希尔方程来描述，最大衰减为69％，半最大浓度（EC（50））为7.4 mM HCO（3-），希尔系数为1.8。平行地，半最大激活（V（h，a））和失活（V（h，i））的电势在10％CO（2）/ 37 mM中以最大移位在超极化方向上线性移动。含有HCO（3）（-）的溶液的V（h，a）（n = 23）为10 +/- 1 mV，V（h，i）（n = 18）为17 +/- 1.4 mV。当在包含相同浓度的碳酸氢盐但含量不同的CO（2）的溶液中诱发电流时，仅观察到无显着变化，而当改变碳酸氢盐且CO（2）保持稳定时，会引起电流的明显变化。实验表明，碳酸氢盐是调节剂，而不是CO（2）。这种碳酸氢盐诱导的调节对于在病理情况下该离子浓度改变（例如过度换气和代谢性酸中毒）的中枢神经系统激发水平可能具有至关重要的意义。

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