Effects of clamp rise-time on rat brain IIA sodium channels in Xenopus oocytes.
Effects of clamp rise-time on rat brain IIA sodium channels in Xenopus oocytes.
复制标题
钳位上升时间对爪蟾卵母细胞大鼠脑 IIA 钠通道的影响。
DOI：
10.1016/s0165-0270(96)02216-9
复制
发表时间：
1997
影响因子：
3
通讯作者：
Rayner,MD
中科院分区：
文献类型：
--
作者：
Ruben,PC;Fleig,A;Featherstone,D;Starkus,JG;Rayner,MD
使用步进去极化和斜坡去极化来模拟双电极电压钳中电压的缓慢稳定时间，研究了切除的大斑块中野生型大鼠脑 IIa 钠通道的动力学特性。超过 1 ms 的斜坡去极化会增强对峰值钠电流 (INa) 的抑制。在步进和斜坡去极化后的切除斑块的宏观钠电流记录中可以看到两种失活率。在缓慢斜坡去极化期间，峰值 INa 的降低与测试脉冲失活最快速率的选择性丧失相关。这种变化可以解释为“快速模式”通道的单独子群失活所致。测试脉冲失活的缓慢速率相对不受改变斜坡持续时间的影响。这些结果足以解释爪蟾卵母细胞钠通道的两电极电压钳记录中典型的缓慢失活动力学。因此，爪蟾卵母细胞中表达的钠通道的动力学不容易通过两电极钳来表征，因为膜电容大并且导致人为地选择慢模式通道的慢钳稳定时间。
The kinetic properties of wild-type rat brain IIa sodium channels in excised macropatches were studied using step depolarizations and ramp depolarizations to imitate the slow settling-time of voltage in two-electrode voltage clamp. Ramp depolarizations longer than 1 ms produce an increasing suppression of peak sodium current (INa). Two rates of inactivation can be seen in macroscopic sodium current records from excised patches following both step and ramp depolarizations. During slow ramp depolarizations, reduction in peak INais associated with selective loss of the fastest rate of test-pulse inactivation. This change can be interpreted as resulting from inactivation of a separate sub-population of `fast mode' channels. The slow rate of test-pulse inactivation is relatively unaffected by changing ramp durations. These results are sufficient to explain the typically slow inactivation kinetics seen in two-electrode voltage clamp recordings of sodium channels in Xenopus oocytes. Thus, the kinetics of sodium channels expressed in Xenopus oocytes are not readily characterizable by two-electrode clamp because of the large membrane capacitance and resulting slow clamp settling time which artifactually selects for slow mode channels.