Effects of intracellular calcium chelation on voltage-dependent and calcium-dependent currents in cat neocortical neurons.
Effects of intracellular calcium chelation on voltage-dependent and calcium-dependent currents in cat neocortical neurons.
复制标题
细胞内钙螯合对猫新皮质神经元电压依赖性和钙依赖性电流的影响。
DOI：
10.1016/0306-4522(92)90166-y
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发表时间：
1992
期刊：
影响因子：
3.3
通讯作者：
Crill,WE
中科院分区：
文献类型：
--
作者：
Schwindt,PC;Spain,WJ;Crill,WE
用KCl和不同浓度的Ca ~（2+）螯合剂1，2-双（邻氨基苯氧基）乙烷-N，N，N′，N′-四乙酸（BAPTA）或其衍生物微电极，穿刺猫感觉运动皮层第V层的大神经元。用含有高BAPTA（200 mM）的电极穿刺迅速消除了Ca 2+依赖性后超极化。棘波参数正常，但通常的时间和电压依赖性整流阈下膜电位是缺席的。正常情况下，这种整流是由两种电压门控电流激活引起的，即持续钠电流（INaP）和超极化内向整流电流（Ih）。这两种电流在使用高BAPTA微电极的电压钳期间都不存在。用含有低BAPTA（2 mM）或衍生物的电极穿刺引起不同的效果。注射1秒的电流脉冲诱发相位放电，而不是通常看到的强直放电。重复放电后的钙依赖性后超极化的幅度和持续时间都比正常大得多。BAPTA衍生物改变细胞后超极化和放电特性的效果与其螯合Ca ~（2+）的效果相似，推测BAPTA的作用是由于降低细胞内Ca ~（2+）浓度所致。高BAPTA的结果表明：（i）INa和Ih都需要最低的细胞内钙浓度才能正常表达，（ii）这些电压门控电流可能受到细胞内钙浓度变化的调节。低BAPTA的结果表明，细胞内钙离子浓度的小幅度降低优先增强缓慢的Ca 2+依赖性K+电流，然后主导细胞的放电特性。转换后的放电特性类似于海马锥体神经元。新皮层和海马锥体神经元类型的反应的差异可能部分取决于内在的Ca 2+缓冲特性的差异。
Large neurons from layer V in a slice preparation of cat sensorimotor cortex were impaled with microelectrodes containing KCl plus different concentrations of the Ca2+chelator1,2-bis(o-aminophenoxy) ethane-N,N,N′,N′-tetra-acetic acid (BAPTA) or two of its derivatives. Impalement with electrodes containing high BAPTA (200 mM) quickly abolished Ca2+-dependent afterhyperpolarizations. Spike parameters were normal, but the usual time- and voltage-dependent rectification of subthreshold membrane potential was absent. Normally, this rectification results from activation of two voltage-gated currents, the persistent sodium current (INaP) and the hyperpolarizing inward rectifier current (Ih). Both of these currents were absent during voltage clamp with high BAPTA microelectrodes. Impalement with electrodes containing low BAPTA (2 mM) or derivatives caused a different effect. Injection of a 1-s current pulse evoked phasic firing instead of the tonic firing seen normally. Both the amplitude and the duration of the Ca2+-dependent afterhyperpolarization that followed repetitive firing were much greater than normal. The effectiveness of BAPTA derivatives in altering afterhyperpolarizations and firing properties were similar to their effectiveness in chelating Ca2+.It is assumed that the BAPTA effects result from reduction of intracellular Ca2+concentration. Results with high BAPTA suggest that (i) bothINaPandIhrequire a minimal intracellular calcium concentration for normal expression, and that (ii) these voltage-gated currents may be modulated by changes in intracellular calcium concentration. Results with low BAPTA suggest that a small reduction of intracellular calcium concentration preferentially enhances a slow, Ca2+-dependent K+current which then dominates the firing properties of the cell. The transformed firing properties resemble those of hippocampal pyramidal neurons. Differences in the responses of neocortical and hippocampal pyramidal neurons types may depend in part on differences in intrinsic Ca2+buffering properties.