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eNeuro. 2016 Jul 20;3(3). pii: ENEURO.0138-16.2016. doi: 10.1523/ENEURO.0138-16.2016. eCollection 2016 May-Jun.

The Possible Role of TASK Channels in Rank-Ordered Recruitment of Motoneurons in the Dorsolateral Part of the Trigeminal Motor Nucleus.

Author information

1
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan; Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
2
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry , Suita, Osaka 565-0871, Japan.
3
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan; Department of Removable Prosthodontics, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
4
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan; Department of Oral Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
5
Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan; Department of Oral Anatomy and Cell Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
6
Department of Pharmacology, Graduate School of Medicine, Osaka University , Suita, Osaka 565-0871, Japan.
7
Department of Vascular Physiology, National Cardiovascular Center Research Institute , Suita, Osaka 565-8565, Japan.
8
Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University , Kyoto 606-8501, Japan.
9
Department of Removable Prosthodontics, Osaka University Graduate School of Dentistry , Suita, Osaka 565-0871, Japan.
10
Department of Orthodontics and Dentofacial Orthopedics , Osaka University Graduate School of Dentistry , Suita, Osaka 565-0871, Japan.

Abstract

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 (two-pore domain weak inwardly rectifying K channel)-related acid-sensitive-K(+) channel (TASK)-1 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 with 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 the soma size of MNs and IR, resting membrane potential, or spike threshold. Dual whole-cell recordings obtained from smaller and larger MNs revealed that the recruitment of MNs depends on their IRs in response to repetitive stimulation of the presumed Ia afferents. 8-Bromoguanosine-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.

KEYWORDS:

TASK channel; input resistance; leak potassium channel; recruitment; trigeminal motoneuron

PMID:
27482536
PMCID:
PMC4951569
DOI:
10.1523/ENEURO.0138-16.2016
[Indexed for MEDLINE]
Free PMC Article

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