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首页> 外文期刊>Journal of Neurophysiology >Slowly inactivating outward currents in a cuticular mechanoreceptor neuron of the cockroach (Periplaneta americana).
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Slowly inactivating outward currents in a cuticular mechanoreceptor neuron of the cockroach (Periplaneta americana).

机译：缓慢灭活蟑螂的表皮机械感受器神经元中的外向电流。

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1. Although rapid adaptation is a widespread feature of sensory receptors, its ionic basis has not been clearly established in any touch receptor, because their small sizes have severely restricted the range of experiments tat can be performed. In the cockroach tactile spine, intracellular voltage-clamp recordings are now possible. 2. The basic electrophysiological properties of the cockroach femoral tactile spine neuron were studied using discontinuous (switching) single-electrode current- and voltage-clamp recordings. A slowly inactivating voltage-sensitive K+ outward current was detected after the major inward currents were blocked with tetrodotoxin. 3. The total outward current activated in < 1 ms at voltages above 0 mV. At moderate depolarizations it did not inactivate, but at higher depolarizations an inactivation time constant of approximately 260 ms was measured. Some recordings also revealed an additional, slower inactivation time constant of approximately 2.5 s. 4. More than half of the voltage-sensitive K+ outward current could be blocked with the Ca2+ channel blockers Co2+ and Cd2+. Tetraethylammonium chloride (TEA) also reduced the amplitude of the outward current to about half of its original amplitude. The actions of both blockers were reversible and probably reflect overlapping blockades of two separate outward currents. 5. The reversal potentials of the currents that remained after block with Co2+ (-91.7 mV) or TEA (-86.8 mV) were both near the K+ equilibrium potential expected for the tactile spine neuron. The voltage dependencies of activation of the Co(2+)- and TEA-resistant currents were both well fitted by Boltzmann distributions, giving values of half maximal activation (V50) equal to -34.5 mV for the Co(2+)-resistant current and -51.3 mV for the TEA-resistant current. 6. Current-clamp recordings revealed that the TEA-sensitive K+ current was the major component of action potential repolarization but that it did not effect the frequency of action potentials evoked by steady depolarization. On the other hand, blockers of Ca(2+)-sensitive K+ currents (Cd2+, Co2+, or charybdotoxin) reduced adaptation and increased the frequency of action potentials significantly but did not effect the duration or amplitude of individual action potentials.
机译：1.尽管快速适应是感觉受体的普遍特征，但其离子基础尚未在任何触摸受体中明确建立，因为它们的小尺寸严重限制了可进行实验的范围。在蟑螂的触觉脊柱中，现在可以进行细胞内电压钳记录。 2.使用不连续（切换）单电极电流和电压钳位记录研究了蟑螂股骨触觉脊柱神经元的基本电生理特性。在河豚毒素阻断了主要的内向电流后，检测到一个缓慢失活的电压敏感的K +外向电流。 3.在大于1 mV的电压下，在<1 ms内激活的总向外电流。在适度的去极化下，它并未失活，但在较高的去极化下，测得的失活时间常数约为260 ms。一些记录还显示了大约2.5 s的另一个较慢的灭活时间常数。 4.可以使用Ca2 +通道阻滞剂Co2 +和Cd2 +阻断一半以上的电压敏感K +外向电流。四乙基氯化铵（TEA）还将向外电流的幅度减小到其原始幅度的一半。两种阻滞剂的作用都是可逆的，可能反映了两个分开的外向流的重叠阻滞。 5.用Co2 +（-91.7 mV）或TEA（-86.8 mV）阻断后剩余的电流反向电位都接近预期的触觉神经元的K +平衡电位。耐Co（2+）和TEA的电流的激活的电压依赖性都通过Boltzmann分布很好地拟合，给出了耐Co（2+）的电流的最大激活（V50）的一半等于-34.5 mV耐TEA电流为-51.3 mV。 6.电流钳记录显示，TEA敏感的K +电流是动作电位复极化的主要组成部分，但它不会影响稳定去极化引起的动作电位的频率。另一方面，对Ca（2+）敏感的K +电流（Cd2 +，Co2 +或charybdotoxin）的阻滞剂可降低适应性并显着增加动作电位的频率，但不影响单个动作电位的持续时间或幅度。

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