THE EFFECT OF INTRACELLULAR CA2+ ON GABA-ACTIVATED CURRENTS IN CEREBELLAR GRANULE CELLS IN CULTURE
THE EFFECT OF INTRACELLULAR CA2+ ON GABA-ACTIVATED CURRENTS IN CEREBELLAR GRANULE CELLS IN CULTURE
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DOI：
10.1007/bf00234942
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发表时间：
1994-11-01
影响因子：
2.4
通讯作者：
CHERUBINI, E
中科院分区：
文献类型：
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作者：
MARTINA, M;KILIC, G;CHERUBINI, E
应用膜片钳技术研究了细胞内游离钙（[Ca ~（2+）]（i））对GABA（A）诱发的小脑颗粒细胞全细胞和单通道电流的影响。通过向细胞外溶液中加入钙离子载体A23187（2 μ M）获得[Ca 2 +]（i）的变化。在存在或不存在A23187的情况下，使用来自Fura-2负载细胞的荧光测量来评估[Ca 2 +]（i）和[Ca 2 +]（o）之间的关系。在2 mM [Ca 2 +]（o）和A23187中，[Ca 2 +]i约为1.5 μ M，而在不存在A23187的情况下，[Ca 2 +]i约为250 nM。在全细胞实验（对称的氯化物浓度）在-50 mV，GABA（0.5 μ M）诱发内向电流，不脱敏。浴应用A23187显着降低了37 +/-6%的GABA电流的稳态振幅。GABA（0.5 μ M）激活的单通道电流也记录在外向配置的膜片钳技术。单通道事件的动力学分析表明，A23187显着增加长关闭时间常数（tau（c3）），而不影响开放时间常数（tau（o 1）和tau（o2））或短和中等关闭时间常数（tau（c1）和tau（c2））。此外，A23187的应用诱导了爆发持续时间（tau（B））的显著减少。我们的结论是A23187升高[Ca ~（2+）]（i）可能降低GABA与GABA（A）受体的结合亲和力。
The patch clamp technique was used to study the effects of intracellular free calcium ([Ca2+](i)) on GABA(A)-evoked whole-cell and single channel currents of cultured cerebellar granule cells. Changes in [Ca2+](i) were obtained by adding to the extracellular solution the calcium ionophore A23187 (2 mu M). The relationship between [Ca2+](i) and [Ca2+](o) in the presence or absence of A23187 was assessed using fluorimetric measurements from Fura-2 loaded cells. In 2 mM [Ca2+](o) and A23187, [Ca2+]i was about 1.5 mu M, whereas in the absence of A23187 it was about 250 nM. In whole-cell experiments (symmetrical chloride concentrations) at -50 mV, GABA (0.5 mu M) evoked inward currents that did not desensitize. Bath application of A23187 significantly reduced the steady-state amplitude of GABA currents by 37 +/- 6%. Single channel currents activated by GABA (0.5 mu M) were also recorded in the outside-out configuration of the patch clamp technique. Kinetic analysis of single channel events revealed that A23187 significantly increased the long closed time constant (tau(c3)) without affecting the open time constants (tau(o1) and tau(o2)) or the short and medium closed time constants (tau(c1) and tau(c2)). Moreover, application of A23187 induced a significant reduction of burst duration (tau(b)). We conclude that a rise in [Ca2+](i) by A23187 may decrease the binding affinity of GABA for the GABA(A) receptor.