Inactivation of calcium currents in granule cells cultured from mouse cerebellum.
Inactivation of calcium currents in granule cells cultured from mouse cerebellum.
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DOI：
10.1113/jphysiol.1991.sp018500
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发表时间：
1991-04
期刊：
影响因子：
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通讯作者：
P. Slesinger;J. Lansman
中科院分区：
文献类型：
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作者：
P. Slesinger;J. Lansman
1.从小鼠小脑分离的细胞在体外生长。在抑制通过Na+和K+通道的电流并使通过Ca 2+通道的电流下降最小化的条件下，用膜片钳技术记录颗粒细胞的Ca 2+通道电流。2.来自超极化保持电位的强去极化电压阶跃产生向内的Ca 2+通道电流，该电流以指数方式衰减至非零水平。内向电流衰减至其峰值幅度的约40%（范围20 - 90%）。3.当Ca ~（2+）被Ba ~（2+）取代或提高细胞外Ba ~（2+）浓度后，内向电流的幅值增加，但电流的衰减速率不受影响。4.电流-电压（I-V）关系显示，峰值或持续电流随着电压脉冲的增加而增加，电压脉冲的正性大于约-30 mV，在+20 mV附近达到最大幅度，并且随着去极化的增加而逐渐变小。5.从正测试脉冲将膜电位快速复极化至-70 mV后产生的尾电流沿沿着单指数时间过程衰减，时间常数约为0.5 ms。在固定复极化电位下测量的尾电流幅度随着前脉冲变得更正而增加，并在前脉冲比+40 mV更正时达到最大值。尾电流的归一化幅度作为前脉冲电位的函数的曲线图与玻尔兹曼关系拟合，其中V1/2 =约+ 8 mV，陡度k = 14 mV。6.将保持电位移到更正的电位降低了由固定电压阶跃引起的Ca 2+通道电流的幅度，并消除了内向电流的衰减。将峰值电流归一化为从非常负的保持电位引起的最大峰值电流，并绘制为保持电位的函数。这些点用Boltzmann关系拟合失活，V1/2 =约-57 mV，陡度k = 14 mV。7.在调节预脉冲持续时间不同的双脉冲实验中研究了灭活的开始。将预脉冲的持续时间增加到固定电位会降低第二个测试脉冲诱发的峰值内向电流。绘制归一化电流与预脉冲持续时间的函数图，结果显示灭活沿着双指数时间过程发展。快时间常数和慢时间常数都随着前脉冲电位变得更正而减小。（400字处截断摘要）
1. Cells dissociated from mouse cerebellum were grown in vitro. Ca2+ channel currents were recorded from granule cells with the patch‐clamp technique under conditions which suppressed currents through Na+ and K+ channels and minimized run‐down of current through Ca2+ channels. 2. A strong depolarizing voltage step from a hyperpolarized holding potential produced inward Ca2+ channel current that decayed exponentially to a non‐zero level. Inward current decayed to approximately 40% of its peak amplitude (range 20‐90%). 3. The inward current increased in amplitude when Ca2+ was replaced with Ba2+ or after raising the concentration of extracellular Ba2+, but the rate of decay of current was unaffected. 4. The current‐voltage (I‐V) relation showed that peak or sustained current increased with voltage pulses more positive than approximately ‐30 mV, reached a maximum amplitude near +20 mV and became progressively smaller with larger depolarizations. 5. The tail currents produced after rapidly repolarizing the membrane potential to ‐70 mV from a positive test pulse decayed along a single exponential time course with a time constant of approximately 0.5 ms. The amplitude of tail current measured at a fixed repolarization potential increased as the pre‐pulse was made more positive and reached a maximum with pre‐pulses more positive than +40 mV. A plot of normalized amplitude of the tail current as a function of the pre‐pulse potential was fitted with a Boltzmann relation with V1/2 = approximately + 8 mV and steepness k = 14 mV. 6. Shifting the holding potential to more positive potentials reduced the amplitude of the Ca2+ channel current elicited by the fixed voltage step and abolished the decay of the inward current. The peak current was normalized to the maximum peak current elicited from a very negative holding potential and plotted as a function of holding potential. The points were fitted with a Boltzmann relation for inactivation with V1/2 = approximately ‐57 mV and steepness k = 14 mV. 7. The onset of inactivation was studied in two‐pulse experiments in which the duration of conditioning pre‐pulse was varied. Increasing the duration of a pre‐pulse to a fixed potential reduced the peak inward current evoked by the second test pulse. Plotting normalized current as a function of pre‐pulse duration showed that inactivation developed along a double exponential time course. Both fast and slow time constants decreased as the pre‐pulse potential was made more positive.(ABSTRACT TRUNCATED AT 400 WORDS)