Exp Neurobiol.  2019 Aug;28(4):451-457. 10.5607/en.2019.28.4.451.

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

• Park SK
• Hong JH
• Jung JK
• Ko HG
• Bae YC

• KMID: 2458543
• DOI: http://doi.org/10.5607/en.2019.28.4.451

Abstract

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.

Keyword

Jaw closing γ-motoneuron; Glutamatergic synapse; Vesicular glutamate transporter; Immunohistochemistry; Electron microscopy

MeSH Terms

Animals
Horseradish Peroxidase
Immunohistochemistry
Isometric Contraction
Membranes
Microscopy, Electron
Mitochondrial Size
Motor Neurons
Presynaptic Terminals
Rats*
Synapses
Vesicular Glutamate Transport Protein 1*
Horseradish Peroxidase
Vesicular Glutamate Transport Protein 1