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

对支配合口肌的三叉神经运动神经核内运动神经元的免疫组织化学分析表明，TASK1和TASK3分别在MNS的胞体和树突中互补表达。实时逆转录聚合酶链式反应显示，大MN(35微米)比小MN(20微米)表达更多的TASK1/cell和TASK3。因此，与较小的MN相比，较大的MN具有更小的输入电阻(IR)和更多的超极化静息膜电位(RMP)。PKG激活促进TASK1活性，抑制TASK3活性。随着MN尺寸的减小，PKG的激活进一步降低了IR，使RMP超极化。α-MnS尺寸的频率分布呈现由较小和较大的α-MnN组成的双峰分布，而Gamma-MnN则呈现较小尺寸的单峰分布。这些发现为闭合下巴运动中运动单位的有序招募提供了重要的分子和细胞基础。

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.