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Abstract：
Sensing of hypoxia and acidosis in arterial chemoreceptors is thought to be mediated through the inhibition of TASK and possibly other (e.g., BKCa ) potassium channels which leads to membrane depolarization, voltage-gated Ca-entry, and neurosecretion. Here, we investigate the effects of pharmacological inhibitors on TASK channel activity and [Ca2+ ]i -signaling in isolated neonatal rat type-1 cells. PK-THPP inhibited TASK channel activity in cell attached patches by up to 90% (at 400 nmol/L). A1899 inhibited TASK channel activity by 35% at 400 nmol/L. PK-THPP, A1899 and Ml 365 all evoked a rapid increase in type-1 cell [Ca2+ ]i . These [Ca2+ ]i responses were abolished in Ca2+ -free solution and greatly attenuated by Ni2+ (2 mM) suggesting that depolarization and voltage-gated Ca2+ -entry mediated the rise in [Ca2+ ]i. Doxapram (50 μmol/L), a respiratory stimulant, also inhibited type-1 cell TASK channel activity and increased [Ca2+ ]i. . We also tested the effects of combined inhibition of BKCa and TASK channels. TEA (5 mmol/L) slightly increased [Ca2+ ]i in the presence of PK-THPP and A1899. Paxilline (300 nM) and iberiotoxin (50 nmol/L) also slightly increased [Ca2+ ]i in the presence of A1899 but not in the presence of PK-THPP. In general [Ca2+ ]i responses to TASK inhibitors, alone or in combination with BKCa inhibitors, were smaller than the [Ca2+ ]i responses evoked by hypoxia. These data confirm that TASK channel inhibition is capable of evoking membrane depolarization and robust voltage-gated Ca2+ -entry but suggest that this, even with concomitant inhibition of BKCa channels, may be insufficient to account fully for the [Ca2+ ]i -response to hypoxia.
摘要：
动脉化学感受器中缺氧和酸中毒的感觉被认为是通过抑制TASK和可能的其他（例如，BKCa）导致膜去极化的钾通道，电压门控Ca进入，和神经分泌。这里,我们研究了药理学抑制剂对分离的新生大鼠1型细胞中TASK通道活性和[Ca2+]i信号传导的影响。PK-THPP抑制细胞附着贴片中的TASK通道活性达90%(在400nmol/L时)。A1899在400nmol/L时抑制了35％的TASK通道活性。PK-THPP,A1899和Ml365均引起1型细胞[Ca2+]i的快速增加。这些[Ca2]i响应在无Ca2溶液中被消除，并被Ni2（2mM）大大减弱，这表明去极化和电压门控的Ca2进入介导了[Ca2]i的升高。多沙普仑(50μmol/L),一种呼吸兴奋剂,还抑制1型细胞TASK通道活性并增加[Ca2]i。.我们还测试了BKCa和TASK通道的联合抑制的效果。在PK-THPP和A1899存在下,TEA(5mmol/L)略微增加[Ca2+]i。在A1899存在下，Paxilline（300nM）和iberiotoxin（50nmol/L）也会稍微增加[Ca2]i，但在PK-THPP存在下不会。一般来说，[Ca2+]i对TASK抑制剂的反应，单独或与BKCa抑制剂联合使用，小于缺氧引起的[Ca2]i反应。这些数据证实了TASK通道抑制能够引起膜去极化和强大的电压门控Ca2-进入，但表明这一点，即使伴随着BKCa通道的抑制，可能不足以完全解释[Ca2]i对缺氧的反应。
