A distinct functional distribution of α and γ motoneurons in the rat trigeminal motor nucleus.
Gamma-motoneurons (γMNs) play a crucial role in regulating isometric muscle contraction. The slow jaw-closing during mastication is one of the most functional isometric contractions, which is developed by the rank-order recruitment of alpha-motoneurons (αMNs) in a manner that reflects the size distribution of αMNs. In a mouse spinal motor nucleus, there are two populations of small and large MNs; the former was identified as a population of γMNs based on the positive expression of the transcription factor estrogen-related receptor 3 (Err3) and negative expression of the neuronal DNA-binding protein NeuN, and the latter as that of αMNs based on the opposite pattern of immunoreactivity. However, the differential identification of αMNs and γMNs in the trigeminal motor nucleus (TMN) remains an assumption based on the size of cell bodies that were retrogradely stained with HRP. We here examined the size distributions of αMNs and γMNs in the dorsolateral TMN (dl-TMN) by performing immunohistochemistry using anti-Err3 and anti-NeuN antibodies. The dl-TMN was identified by immunopositivity for vesicular glutamate transporter-1. Immunostaining for choline acetyltransferase and Err3/NeuN revealed that the dl-TMN is composed of 65% αMNs and 35% γMNs. The size distribution of αMNs was bimodal, while that of γMNs was almost the same as that of the population of small αMNs, suggesting the presence of αMNs as small as γMNs. Consistent with the size concept of motor units, the presence of smaller jaw-closing αMNs was coherent with the inclusion of jaw-closing muscle fibers with smaller diameters compared to limb muscle fibers.
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.|Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Yukako
Y
Morita-Isogai
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Hajime
H
Sato
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.|Department of Oral Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima, 890-8544, Japan.
Mitsuru
M
Saito
Department of Oral Anatomy and Cell Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima, 890-8544, Japan.|Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan.
Eriko
E
Kuramoto
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Dong Xu
DX
Yin
Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan.
Takeshi
T
Kaneko
Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Takashi
T
Yamashiro
Department of Orthodontics, Faculty of Dentistry, National University of Singapore, 11 Lower Kent Ridge Road, Singapore, 119083, Singapore.
Kenji
K
Takada
Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, 28 Yeongeon-Dong, Jongno-Gu, Seoul, 110-749, Republic of Korea.
Seog Bae
SB
Oh
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Hiroki
H
Toyoda
Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan. kang@dent.osaka-u.ac.jp.|Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, 28 Yeongeon-Dong, Jongno-Gu, Seoul, 110-749, Republic of Korea. kang@dent.osaka-u.ac.jp.
Youngnam
Y
Kang
D000818:Animals; D002452:Cell Count / Q000379:methods; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D051272:Glucose Transporter Type 1 / Q000378:metabolism; D008297:Male; D009046:Motor Neurons / Q000145:classification* / Q000502:physiology*; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000378:metabolism; D066266:Trigeminal Motor Nucleus / Q000166:cytology*; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
D051272:Glucose Transporter Type 1; D011960:Receptors, Estrogen; C495678:Slc2a1 protein, mouse; D050598:Vesicular Glutamate Transport Protein 1; D002795:Choline O-Acetyltransferase; D010751:Phosphopyruvate Hydratase
Alpha-motoneuron; Err3; Gamma-motoneuron; NeuN; Trigeminal motor nucleus