Moritz Anna T, Newkirk Gregory, Powers Randall K, Binder Marc D
Department of Physiology and Biophysics,School of Medicine, University of Washington, Seattle, Washington 98195-7290, USA.
J Neurophysiol. 2007 Aug;98(2):1042-7. doi: 10.1152/jn.01294.2006. Epub 2007 May 23.
Voltage-dependent persistent inward currents (PICs) make an important contribution to the input-output properties of alpha motoneurons. PICs are thought to be mediated by membrane channels located primarily on the dendrites as evidenced by prolonged tail currents following the termination of a voltage step and by a clockwise hysteresis in the whole cell inward currents recorded in response to depolarizing then repolarizing voltage ramp commands. We report here, however, that voltage-clamp currents with these same features can be generated in isolated somatic membrane patches from rat hypoglossal motoneurons. Long-lasting (200-800 ms) tail currents after 1-s voltage-clamp pulses were observed in nucleated patches from 16 of 23 cells. Further, these somatic PICs display "facilitation" in response to conditioning depolarization as previously observed in whole cell recordings from intact neurons. Pharmacological tests suggest that the PICs were primarily mediated by Cav1 channels. Our results show that many of the features of persistent calcium currents recorded from intact motoneurons do not necessarily reflect a remote dendritic origin but can also be ascribed to the intrinsic properties of their Cav1 channels.
电压依赖性持续性内向电流（PICs）对α运动神经元的输入-输出特性有重要贡献。PICs被认为主要由位于树突上的膜通道介导，这一点可由电压阶跃终止后的延长尾电流以及响应去极化然后复极化电压斜坡指令记录的全细胞内向电流中的顺时针滞后现象证明。然而，我们在此报告，具有这些相同特征的电压钳电流可在大鼠舌下运动神经元的分离体细胞膜片中产生。在23个细胞中的16个细胞的有核膜片中观察到1秒电压钳脉冲后的持久（200 - 800毫秒）尾电流。此外，这些体细胞PICs对条件性去极化表现出“易化”，正如之前在完整神经元的全细胞记录中所观察到的那样。药理学测试表明，PICs主要由Cav1通道介导。我们的结果表明，从完整运动神经元记录的持续性钙电流的许多特征不一定反映遥远的树突起源，也可归因于其Cav1通道的内在特性。
