Modulation of rank-ordered recruitment of motor units in the jaw-closing movement by leak K+ channels

对支配闭颌肌的三叉神经运动核中的运动神经元（MN）的免疫组织化学分析显示，TASK 1和TASK 3分别在MN的索马体和树突中互补表达。实时RT PCR显示，与小MN（<20 μ m）相比，大MN（>35 μ m）表达更多的TASK 1/细胞和TASK 3。因此，与较小的MN相比，较大的MN具有较小的输入电阻（IR）和更多的超极化静息膜电位（RMP）。PKG激活增强TASK 1活性，同时抑制TASK 3活性。随着MN尺寸变小，PKG激活更多地降低IR并使RMP超极化。发现α-MN的大小的频率分布显示由较小和较大的α-MN组成的双峰分布，而γ-MN显示较小尺寸的单峰图案。这些发现提供了关键的分子和细胞基础的排名有序募集的运动单位在下颌闭合运动。

The immunohistochemical analysis of motoneurons (MNs) in the trigeminal motor nucleus that innervates jaw-closing muscles revealed that TASK1 and TASK3 are complementary expressed in the soma and dendrites of MNs, respectively. The real-time RT PCR revealed that large MNs (>35 microm) expressed more TASK1/cell and TASK3 compared to small MNs (<20 microm). Consequently, larger MNs had smaller input resistance (IR) and more hyperpolarized resting membrane potentials (RMP) compared to smaller MNs. PKG activation enhanced TASK1 activity while it inhibited TASK3 activity. As the MN size becomes smaller, PKG activation more decreased the IR and hyperpolarized the RMP. The frequency distribution of sizes of alpha-MNs was found to display a bimodal distribution composed of smaller and larger alpha-MNs while gamma-MNs displayed a unimodal patter of smaller size. These finding provide crucial molecular and cellular bases of the rank-ordered recruitment of motor units in the jaw-closing movement.