Ultrastructural analysis of glutamate-, GABA-, and glycine-immunopositive boutons from supratrigeminal premotoneurons in the rat trigeminal motor nucleus.
The supratrigeminal region (Vsup) is important for coordination of smooth jaw movement. However, little is known about the synaptic connections of the Vsup premotoneurons with the trigeminal motor neurons. In the present study, we examined axon terminals of Vsup premotoneurons in the contralateral trigeminal motor nucleus (Vmo) by a combination of anterograde tracing with cholera toxin B-horseradish peroxidase (CTB-HRP), postembedding immunohistochemistry for the amino acid transmitters glutamate, GABA, and glycine, and electron microscopy. Tracer injections resulted in anterograde labeling of axon terminals of the Vsup premotoneurons in the motor trigeminal nucleus (Vmo). The labeled boutons in Vmo exhibited immunoreactivity for glutamate, GABA, or glycine: glutamate-immunopositive boutons (69%) were more frequently observed than GABA- or glycine-immunopositive boutons (19% and 12%, respectively). Although most labeled boutons (97%) made synaptic contacts with a single postsynaptic dendrite, a few glutamate-immunopositive boutons (3%) showed synaptic contact with two dendrites. No labeled boutons participated in axoaxonic synaptic contacts. Most labeled boutons (78%) were presynaptic to dendritic shafts, and the remaining 22% were presynaptic to somata or primary dendrites. A large proportion of GABA- or glycine-immunopositive boutons (40%) were presynaptic to somata or primary dendrites, whereas most glutamate-immunopositive boutons (86%) were presynaptic to dendritic shafts. These results indicate that axon terminals of Vsup premotoneurons show simple synaptic connection with Vmo neurons. This may provide the anatomical basis for the neural information processing responsible for jaw movement control.
Paik
Sang Kyoo
SK
Department of Oral Anatomy and Neurobiology, School of Dentistry, BK21, Kyungpook National University, Daegu, Korea.
Lee
Hyo Jeong
HJ
Choi
Min Ki
MK
Cho
Yi Sul
YS
Park
Mae Ja
MJ
Moritani
Masayuki
M
Yoshida
Atsushi
A
Kim
Yun Sook
YS
Bae
Yong Chul
YC
D000818:Animals; D002772:Cholera Toxin / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D005998:Glycine / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D008845:Microinjections; D008854:Microscopy, Electron; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014278:Trigeminal Nuclei / Q000378:metabolism / Q000648:ultrastructure*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D002772:Cholera Toxin; D006735:Horseradish Peroxidase; D005998:Glycine