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2005

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J. Huguenard;David A. Prince

1.用全细胞电压钳技术记录了酶法分离的大鼠丘脑中继神经元的钙电流。2.低阈值和高阈值的钙电流引起的去极化电压阶跃从保持电位更负超过-60 mV。类似于感觉神经元中的T电流的瞬态电流在接近-65 mV的低阈值下被激活，并且在高达-35 mV的命令步骤下完全失活。电压阶跃到更多去极化水平激活了高阈值电流，该电流在200 ms阶跃去极化期间缓慢且不完全地失活。3.高阈值电流包含非失活和缓慢失活两种成分，它们分别对保持电位不敏感和敏感。4. A 'T型'电流是突出的继电器神经元，在绝对值（350 pA峰值电流平均值）和高阈值电流。最大瞬态电流与最大持续电流的平均比值大于2。5. T电流可以以类似于用于快速Na+电流潜在动作电位产生的方式建模，使用m3 h格式。T-电流的激活速率与电压有关，时间常数为T。在23 ℃下，在-60至-10 mV的命令电位下，在8和2 ms之间变化。失活的速率也是电压依赖性的，并且在相同的电压范围内，时间常数Th在50和20 ms之间变化。当指令电位大于-35 mV时，钙电流失活不再符合单一指数。6. T电流的稳态失活可用Boltzman方程拟合，斜率因子为6-3，半失活电压为83-5 mV。7. T-电流失活的恢复不是指数的。回收率的主要成分（占总量的70-80%）在比-90 mV更负的电位下不是非常电压敏感的，在-92 mV和23 ° C下Tr为251 ms，相比之下，

1. Calcium currents were recorded with whole-cell voltage-clamp procedures in relay neurones of the rat thalamus which had been acutely isolated by an enzymatic dissociation procedure. 2. Low-threshold and high-threshold Ca2+ currents were elicited by depolarizing voltage steps from holding potentials more negative than -60 mV. A transient current, analogous to the T-current in sensory neurones, was activated at low threshold near -65 mV and was completely inactivating at command steps up to -35 mV. Voltage steps to more depolarized levels activated a high-threshold current that inactivated slowly and incompletely during a 200 ms step depolarization. 3. The high-threshold current contained both non-inactivating and slowly inactivating components which were insensitive and sensitive to holding potential, respectively. 4. A 'T-type' current was prominent in relay neurones, in both absolute terms (350 pA peak current average) and in relation to high-threshold currents. The average ratio of maximum transient to maximum sustained current was greater than 2. 5. T-current could be modelled in a manner analogous to that employed for the fast Na+ current underlying action potential generation, using the m3h format. The rate of activation of T-current was voltage dependent, with a time constant (T.) varying between 8 and 2 ms at command potentials of -60 to -10 mV at 23 'C. The rate of inactivation was also voltage dependent, and the time constant Th varied between 50 and 20 ms over the same voltage range. With command potentials more positive than -35 mV, the inactivation of Ca2+ current could no longer be fitted by a single exponential. 6. Steady-state inactivation of T-current could be well fitted by a Boltzman equation with slope factor of 6-3 and half-inactivated voltage of 83-5 mV. 7. Recovery from inactivation of T-current was not exponential. The major component of recovery (70-80% of total) was not very voltage sensitive at potentials more negative than -90 mV, with Tr of 251 ms at -92 mV and 23 'C, compared to

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