Inhibitory gating modulation of small conductance Ca2+-activated K+ channels by the synthetic compound (R)-N-(benzimidazol-2-yl)-1,2,3,4-tetrahydro-1-naphtylamine (NS8593) reduces afterhyperpolarizing current in hippocampal CA1 neurons
Inhibitory gating modulation of small conductance Ca2+-activated K+ channels by the synthetic compound (R)-N-(benzimidazol-2-yl)-1,2,3,4-tetrahydro-1-naphtylamine (NS8593) reduces afterhyperpolarizing current in hippocampal CA1 neurons
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DOI：
10.1124/mol.106.027110
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发表时间：
2006-11-01
影响因子：
3.6
通讯作者：
Christophersen, Palle
中科院分区：
文献类型：
--
作者：
Strobaek, Dorte;Hougaard, Charlotte;Christophersen, Palle
SK通道是一种小电导钙激活的K+通道，对神经元兴奋性的控制、放电模式的微调和突触机制的调节都很重要。经典的SK通道药理学主要集中在多肽阿帕明上，它通过堵塞毛孔的机制在细胞外发挥作用。1-乙基-2-苯并咪唑烷酮(1-EBIO)和6，7-二氯-1H-吲哚-2，3-二酮-3-肟(NS309)是增强SK通道表观钙敏感性的正向门控调节剂。在本研究中，我们将抑制门控调制描述为选择性抑制SK通道的一种新原理。在全细胞膜片钳实验中，化合物(R)-N-(苯并咪唑-2-基)-1，2，3，4-四氢-1-萘胺(NS8593)可逆性地抑制SK3介导的重组电流(人SK3和大鼠SK3)，其作用约100 nM。然而，与已知的孔道阻滞剂不同，NS8593不抑制I-125-阿帕明的结合。切除斑块实验表明，NS8593使钙激活曲线右移，降低了钙敏感性，但对最大钙激活的SK电流影响不大。NS8593对SK1-3各亚型均呈钙依赖性抑制(0.5mM时K-d分别为0.42、0.60和0.73mU)，而对钙激活的中等电导和大电导K+通道(分别为HIK和HBK通道)无影响。作用部位可以从膜的两侧到达，在高浓度的正向调节剂NS309存在下，NS8593介导的抑制被阻止。NS8593进一步在小鼠海马片CA1神经元上进行了实验，结果表明，NS8593在3mM的浓度下可抑制阿帕明和微管胡萝卜碱敏感的SK介导的后超极化电流。
SK channels are small conductance Ca2+-activated K+ channels important for the control of neuronal excitability, the fine tuning of firing patterns, and the regulation of synaptic mechanisms. The classic SK channel pharmacology has largely focused on the peptide apamin, which acts extracellularly by a pore-blocking mechanism. 1-Ethyl-2-benzimidazolinone ( 1-EBIO) and 6,7-dichloro-1H-indole-2,3-dione 3-oxime ( NS309) have been identified as positive gating modulators that increase the apparent Ca2+ sensitivity of SK channels. In the present study, we describe inhibitory gating modulation as a novel principle for selective inhibition of SK channels. In whole-cell patch-clamp experiments, the compound ( R)-N-( benzimidazol-2-yl)- 1,2,3,4-tetrahydro-1-naphtylamine ( NS8593) reversibly inhibited recombinant SK3-mediated currents ( human SK3 and rat SK3) with potencies around 100 nM. However, in contrast to known pore blockers, NS8593 did not inhibit I-125-apamin binding. Using excised patches, it was demonstrated that NS8593 decreased the Ca2+ sensitivity by shifting the activation curve for Ca2+ to the right, only slightly affecting the maximal Ca2+-activated SK current. NS8593 inhibited all the SK1-3 subtypes Ca2+-dependently ( K-d = 0.42, 0.60, and 0.73 mu M, respectively, at 0.5 mu M Ca2+), whereas the compound did not affect the Ca2+-activated K+ channels of intermediate and large conductance ( hIK and hBK channels, respectively). The site of action was accessible from both sides of the membrane, and the NS8593-mediated inhibition was prevented in the presence of a high concentration of the positive modulator NS309. NS8593 was further tested on mouse CA1 neurons in hippocampal slices and shown to inhibit the apamin- and tubocurarine-sensitive SK-mediated afterhyperpolarizing current, at a concentration of 3 mu M.