Articles

Article

Short Communication

Exp Neurobiol. 2019; 28(4): 451-457

Published online August 31, 2019

https://doi.org/10.5607/en.2019.28.4.451

© The Korean Society for Brain and Neural Sciences

Vesicular Glutamate Transporter 1 (VGLUT1)- and VGLUT2-containing Terminals on the Rat Jaw-closing γ-Motoneurons

Sook Kyung Park1†, Jae Hyun Hong1†, Jae Kwang Jung2, Hyoung-Gon Ko1 and Yong Chul Bae1*

Departments of 1Anatomy and Neurobiology, 2Oral Medicine, School of Dentistry, Kyungpook National University, Daegu 41940, Korea

Correspondence to: TEL: 82-53-660-6860, FAX: 82-53-426-7731
e-mail: ycbae@knu.ac.kr
S.K. Park and J.H. Hong contributed equally to this work.

Received: April 6, 2019; Revised: May 22, 2019; Accepted: July 8, 2019

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License
(http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and
reproduction in any medium, provided the original work is properly cited.

Currently, compared to jaw-closing (JC) α-motoneurons, the information on the distribution and morphology of glutamatergic synapses on the jaw-closing (JC) γ-motoneurons, which may help elucidate the mechanism of isometric contraction of the JC muscle, is very limited. This study investigated the distribution and ultrastructural features of vesicular glutamate transporter 1 (VGLUT1)- and VGLUT2-immunopositive (+) axon terminals (boutons) on JC γ-motoneurons by retrograde tracing with horseradish peroxidase, electron microscopic immunocytochemistry, and quantitative analysis. About 35% of the boutons on identified JC γ-motoneurons were VGLUT+, and of those, 99% were VGLUT2+. The fraction of VGLUT1+ boutons of all boutons and the percentage of membrane of JC γ-motoneurons covered by these boutons were significantly lower than those for the JC α-motoneurons, revealed in our previous work. The bouton volume, mitochondrial volume, and active zone area of the VGLUT2+ boutons on the JC γ-motoneurons were uniformly small. These findings suggest that the JC γ-motoneurons, in contrast to the JC α-motoneurons, receive generally weak glutamatergic synaptic input almost exclusively from VGLUT2+ premotoneurons that form direct synapse with motoneurons.

Graphical Abstract


Keywords: Jaw closing γ-motoneuron, Glutamatergic synapse, Vesicular glutamate transporter, Immunohistochemistry, Electron microscopy