State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, PR China.
Neuroscience. 2010 Sep 15;169(4):1548-56. doi: 10.1016/j.neuroscience.2010.06.026. Epub 2010 Jun 25.
The presence of large-conductance Ca(2+)-activated potassium (BK) channels, which are considered to play an important role in the excitability of neurons, in the highly-excitable lateral globus pallidus (LGP) neurons has yet to be confirmed. In this study, we confirmed the functional expression of BK channels in mouse LGP neurons and investigated the characteristics of their single-channel currents using inside-out patch-clamp recordings. These BK channels had a conductance of 276 pS, were activated by the elevation of both the transmembrane potential and intracellular calcium concentration (Ca(2+)), and were completely blocked by the BK channel-specific blocker paxilline (100 nM). In addition, the channel currents were sensitive to high-energy phosphate compounds and low internal pH. The cellular function of these BK channels was then investigated by nystatin-perforated whole-cell recording. Paxilline (100 nM) had no effect on the frequency and half-width of the action potential (AP) in LGP neurons under control conditions, but significantly attenuated the hyperpolarization that was caused by carbonyl cyanide m-chlorophenylhydrazone (CCCP), an inhibitor of ATP synthesis. In addition, the pancreatic beta-cell type ATP-sensitive potassium channel (K(ATP) channel) blocker tolbutamide (0.25 mM) also attenuated the hyperpolarization, in a manner similar to paxilline. The voltage-dependent potassium channel blocker tetraethylammonium (TEA, 2 mM) significantly decreased the frequency and increased the half-width of the AP in LGP neurons under control conditions, and attenuated CCCP-induced hyperpolarization to an extent close to that of paxilline. The results presented here suggest that functional BK channels are present in LGP neurons, and may behave as partners of K(ATP) channels in the regulation of neuronal activity under metabolic stress conditions.
大电导钙激活钾 (BK) 通道被认为在神经元兴奋性中发挥重要作用，但其在高度兴奋的外侧苍白球 (LGP) 神经元中的存在尚未得到证实。在这项研究中，我们证实了 BK 通道在小鼠 LGP 神经元中的功能性表达，并通过内面向外膜片钳记录研究了其单通道电流的特性。这些 BK 通道的电导为 276 pS，可被跨膜电位和细胞内钙离子浓度 (Ca(2+)) 的升高激活，并被 BK 通道特异性阻断剂巴氯芬 (100 nM) 完全阻断。此外，通道电流对高能磷酸化合物和低细胞内 pH 值敏感。然后通过制霉菌素穿孔全细胞记录研究了这些 BK 通道的细胞功能。在对照条件下，巴氯芬 (100 nM) 对 LGP 神经元动作电位 (AP) 的频率和半宽度没有影响，但显著减弱了三氯苯甲酰基氰化物 (CCCP) 引起的超极化，CCCP 是一种 ATP 合成抑制剂。此外，胰岛β细胞类型的 ATP 敏感性钾通道 (K(ATP) 通道) 阻断剂甲苯磺丁脲 (0.25 mM) 也以类似于巴氯芬的方式减弱了超极化。电压依赖性钾通道阻断剂四乙铵 (TEA，2 mM) 在对照条件下显著降低了 LGP 神经元中 AP 的频率并增加了其半宽度，并减弱了 CCCP 诱导的超极化，程度接近巴氯芬。本研究结果表明，功能性 BK 通道存在于 LGP 神经元中，并且在代谢应激条件下可能作为 K(ATP) 通道的伙伴参与神经元活动的调节。
