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

• Published in: Experimental neurobiology Vol. 28; no. 4; pp. 451 - 457
• Main Authors: Park, Sook Kyung, Hong, Jae Hyun, Jung, Jae Kwang, Ko, Hyoung-Gon, Bae, Yong Chul
• Format: Journal Article
• Language: English
• Published: Korea (South) The Korean Society for Brain and Neural Sciences 31.08.2019; 한국뇌신경과학회
• Subjects: Short Communication; 뇌과학; Immunohistochemistry; Electron microscopy; Glutamatergic synapse; Jaw closing γ-motoneuron; Vesicular glutamate transporter
• ISSN: 1226-2560; 2093-8144
• DOI: 10.5607/en.2019.28.4.451

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.