Electrophysiological properties of sodium current subtypes in small cells from adult rat dorsal roof ganglia
Electrophysiological properties of sodium current subtypes in small cells from adult rat dorsal roof ganglia
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DOI：
10.1111/j.1469-7793.1998.771bg.x
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发表时间：
1998-09-15
影响因子：
5.5
通讯作者：
Elliott, JR
中科院分区：
文献类型：
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作者：
Rush, AM;Bräu, ME;Elliott, JR
1.全细胞和单通道Na+电流记录从小（约。20 μ m直径）细胞。电流进行了分类，其敏感性0.3 μ M河豚毒素（TTX），电生理特性和单通道振幅。根据记录到的电流类型对细胞进行分类. A型细胞基本上表达纯TTX-S电流。预脉冲持续时间在50 ms和1 s之间的可用性实验给出了约-65 mV的半可用电压（V-h），但可用性曲线通常具有复杂的形状，与多个灭活过程一致。测定的失活时间常数范围从小于1 ms到超过100 s，取决于使用的协议。除了TTX-S电流外，细胞类型B和C各自还具有大量不同的TTX-R电流，我们分别将其命名为TTX-R1和TTX-R2。TTX-R1电流的1 s V-h为-29 mV，在-67 mV下显示出很小的1 Hz使用依赖性，并从60 ms去极化脉冲诱导的失活中恢复，时间常数为1.6 ms（91%）和908 ms。它们还显示出缓慢的失活过程，组分时间常数约为10和100 s。TTX-R2电流在更负的电位（1 s V-h = -46 mV）下激活和失活，显示出显著的1 Hz使用依赖性，在-67 mV下失活（60 ms脉冲）恢复时间常数为3.3 ms（58%）和902 ms。D型细胞在0.3 μ M TTX中，在-67 mV的保持电位下几乎没有或没有电流。当保持电位变为-107 mV时，电流幅度增加。D型细胞电流的超极化可用性和I-V曲线甚至比TTX-R2电流更大，提示TTX-R3通道的存在.在含有250 mM外部NaCl的外向贴片中，TTX-S通道的单通道电导（γ）为19.5 pS，半最大激活电位（V-a）为-45 mV。TTX-R通道的一个群体具有9.2 pS的γ和-27 mV的V-a。第二群体具有16.5pS的γ和-42mV的更负的V-a。后者可能是D型细胞电流的基础。小DRG细胞表达多种Na+电流，具有不同的时间常数和激活和失活的电压依赖性。伤害性细胞仍然火灾时，慢性去极化增加外部K+浓度。TTX-R1和TTX-R2 Na+通道可能支持这种放电，而本文所述的失活时间常数范围通常会增加DRG细胞爆发放电行为的库。
1. Whole-cell and single-channel Na+ currents were recorded from small (ca. 20 mu m diameter) cells isolated from adult rat dorsal root ganglia (DRG). Currents were classified by their sensitivity to 0.3 mu M tetrodotoxin (TTX), electrophysiological properties and single-channel amplitude. Cells were classified according to the types of current recorded from them.2. Type A cells expressed essentially pure TTX-sensitive (TTX-S) currents. Availability experiments with prepulse durations between 50 ms and 1 s gave a half-available voltage (V-h) of around -65 mV but the availability curves often had a complex shape, consistent with multiple inactivation processes. Measured inactivation time constants ranged from less than 1 ms to over 100 s, depending on the protocol used.3. Cell types B and C each had, in addition to TTX-S currents, substantial and different TTX-resistant (TTX-R) currents that we have designated TTX-R1 and TTX-R2, respectively. TTX-R1 currents had a 1 s V-h of -29 mV, showed little 1 Hz use dependence at -67 mV and recovered from the inactivation induced by a 60 ms depolarizing pulse with time constants of 1.6 ms (91 %) and 908 ms. They also exhibited slow inactivation processes with component time constants around 10 and 100 s. TTX-R2 currents activated and inactivated at more negative potentials (1 s V-h = -46 mV), showed substantial 1 Hz use dependence and had inactivation (60 ms pulse) recovery time constants at -67 mV of 3.3 ms (58 %) and 902 ms.4. Type D cells had little or no current in 0.3 mu M TTX at a holding potential of -67 mV. Current amplitude increased on changing the holding potential to -107 mV. Type D cell currents had more hyperpolarized availability and I-V curves than even TTX-R2 currents and suggest the existence of TTX-R3 channels.5. In outside-out patches with 250 mM external NaCl, the single-channel conductance (gamma) of TTX-S channels was 19.5 pS and the potential for half-maximal activation (V-a) was -45 mV. One population of TTX-R channels had a gamma of 9.2 pS and a V-a of -27 mV. A second population had a gamma of 16.5 pS and a more negative V-a of -42 mV. The latter population may underlie the type D cell current.6. Small DRG cells express multiple Na+ currents with varied time constants and voltage dependences of activation and inactivation. Nociceptive cells still fire when chronically depolarized by an increased external K+ concentration. TTX-R1 and TTX-R2 Na+ channels may support that firing, while the range of inactivation time constants described here would increase the repertoire of DRG cell burst firing behaviour generally.