Somatic sodium channels of frog olfactory receptor neurones are inactivated at rest.
Somatic sodium channels of frog olfactory receptor neurones are inactivated at rest.
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青蛙嗅觉受体神经元的体细胞钠通道在休息时失活。
DOI：
10.1007/bf00497779
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Gesteland,RC
中科院分区：
文献类型：
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作者：
Pun,RY;Gesteland,RC
用全细胞“紧密封闭”膜片记录技术研究了急性分离的草蛙嗅觉感受器神经元的膜兴奋性。蛙卵的平均静息膜电位为−52 mV，平均输入电阻为1-2GΩ，平均电容为4.5pF。在所研究的大多数细胞中(超过70%)，在超极化脉冲结束时或注入电流使膜电位超极化后，可诱发出持续时间较短(几毫秒)的动作电位。在电压钳制条件下，膜的去极化可以引起快速的内向电流和外向电流。快内向电流以1-2ms的时间常数衰减，电压每升高52 mV，快内向电流下降e倍，并被选择性电压依赖性钠通道阻滞剂河豚毒素(0.5-1μM)阻断。稳态失活研究表明，半失活的平均电压(V1/2)为−82 mV(范围为−72~−98 mV)，这表明在静止膜电位下，蛙卵细胞胞体或胞体的电压依赖性Na+通道不能用于传导电流。这一发现提出了一种可能性，即电压依赖的Na+通道可能在胞体的感觉转导中不起重要作用。我们的结果表明，青蛙的喙在向大脑传递信号方面非常有效，因为在纤毛上产生的电流将引导轴突去极化。这些数据也可以解释在活体细胞外记录实验中遇到的单细胞动作电位数量较少的原因。
Membrane excitability of acutely isolated olfactory receptor neurones (ORNs) of the grass frog (R. pipiens) was studied with the use of the whole-cell “tight-seal” patch recording technique. ORNs of the frog had a mean resting membrane potential of −52 mV, a mean input resistance of 1–2 GΩ, and a mean capacitance of 4.5 pF. In the majority of cells examined (over 70%), short duration (several milliseconds) action potentials were elicited at the end of a hyperpolarising pulse (offspike) or following hyperpolarization of the membrane potential by injection of current. Under voltage-clamp conditions, a fast inward current followed by an outward current could be evoked upon depolarisation of the membrane. The fast inward current decayed with a time constant of 1–2 ms, with an e-fold decrease per 52 mV increase in voltage, and was blocked by the selective voltage-dependent sodium channel blocker tetrodotoxin (0.5–1 μM). Steady-state inactivation studies revealed that the mean voltage for half-inactivation (V1/2) was −82 mV (range −72 to −98 mV), which indicates that the voltage-dependent Na+channels in the cell body or soma of frog ORNs are not available for conducting currents at the resting membrane potential. This finding raises the possibility that voltage-dependent Na+channels may not play a significant role in sensory transduction at the soma. Our results indicate that ORNs of the frog are very efficient in transducing signals towards the brain since currents generated at the cilia will be directed towards depolarising the axon. The data also could account for the low number of single-cell action potentials encountered in extracellular recording experiments in vivo.