RT Journal Article
SR Electronic
T1 The possible role of TASK channels in rank-ordered recruitment of motoneurons in the dorsolateral part of the trigeminal motor nucleus
JF eneuro
JO eneuro
FD Society for Neuroscience
SP ENEURO.0138-16.2016
DO 10.1523/ENEURO.0138-16.2016
A1 Keiko Okamoto
A1 Norihito Emura
A1 Hajime Sato
A1 Yuki Fukatsu
A1 Mitsuru Saito
A1 Chie Tanaka
A1 Yukako Morita
A1 Kayo Nishimura
A1 Eriko Kuramoto
A1 Dong Xu Yin
A1 Kazuharu Furutani
A1 Makoto Okazawa
A1 Yoshihisa Kurachi
A1 Takeshi Kaneko
A1 Yoshinobu Maeda
A1 Takashi Yamashiro
A1 Kenji Takada
A1 Hiroki Toyoda
A1 Youngnam Kang
YR 2016
UL http://www.eneuro.org/content/early/2016/07/07/ENEURO.0138-16.2016.abstract
AB Because a rank-ordered recruitment of motor units occurs during isometric contraction of jaw-closing muscles, jaw-closing motoneurons (MNs) may be recruited in a manner dependent on their soma sizes or input resistances (IRs). In the dorsolateral part of the trigeminal motor nucleus (dl-TMN) in rats, MNs abundantly express TWIK-related acid-sensitive-K+ channel-1 (TASK1) and TASK3 channels, which determine the IR and resting membrane potential. Here we examined how TASK channels are involved in IR-dependent activation/recruitment of MNs in the rat dl-TMN by using multiple methods. The real-time PCR study revealed that single large MNs (> 35 μm) expressed TASK1 and TASK3 mRNAs more abundantly compared to single small MNs (15–20 μm). The immunohistochemistry revealed that TASK1 and TASK3 channels were complementarily distributed in somata and dendrites of MNs, respectively. The density of TASK1 channels seemed to increase with a decrease in soma diameter while there were inverse relationships between soma size of MNs and IR, resting membrane potential or spike threshold. Dual whole-cell recordings obtained from a smaller and larger MNs revealed that MNs are recruited depending on their IRs in response to repetitive stimulation of the presumed Ia afferents. 8-Br-cGMP decreased IRs in small MNs while it hardly changed those in large MNs, and subsequently decreased the difference in spike onset latency between the smaller and larger MNs, causing a synchronous activation of MNs. These results suggest that TASK channels play critical roles in rank-ordered recruitment of MNs in the dl-TMN.Significance Statement: The mastication of foods occurs during the slow-closing phase of the mastication cycle, in which isometric contraction of jaw-closing muscles is developed through the rank-ordered recruitment of jaw-closing motoneurons (MNs). However, its molecular mechanism remains unknown. Here we show that TWIK-related acid-sensitive-K+ channel-1 (TASK1) and TASK3 channels, which determine the input resistance and resting membrane potential, are differentially expressed between small and large MNs and play critical roles in the rank-ordered recruitment of jaw-closing MNs. The principle of the rank-ordered recruitment was originally proposed based on the conduction velocity of the motor nerve fibers innervating a set of muscle fibers. After a half-century, we for the first time disclosed the molecular mechanism for the rank-ordered recruitment of jaw-closing MNs.