Central projection of proprioceptive afferents arising from maxillo-facial regions in some animals studied by HRP-labeling technique.
20 ICR mice (adult females) were used for analyzing the axonal projection of the trigeminal mesencephalic tract neurons and 10 Japanese shrew-moles for analyzing that of the snout proprioceptive neurons. The HRP-labeled axons were found to be ipsilaterally terminated in the trigeminal motor nucleus, supratrigeminal nucleus and trigeminal main and spinal tract nuclei, lateral pontine-medullary reticular formation, vagal dorsal motor and hypoglossal nuclei and the lamina V of the C2 spinal cord segments. No HRP-labeled axons were found in the facial and solitary nuclei and the cerebellum. Also, the functional localization of the trigeminal mesencephalic tract neurons was analyzed with the retrograde tracers of fluorescent compounds injected into the jaw-closing muscles having spindles. The fluorescent-labeled neurons were found to be intermingled throughout the nucleus and clustered at the caudal level of the nucleus. Also, double or triple fluorescent-labeled neurons were not observed in the nucleus. The HRP-labeled axon bundle of the facial proprioceptive neurons are divided rostro-caudally into the shorter ascending and the longer descending roots, both running closely dorsal to the trigeminal spinal tract nucleus. The ascending root lies adjacently dorsal to the spinal tract nucleus, giving off the terminal fibers to it, to the wider area of the dorso-medial pontine nuclei and finally to the cerebellar nuclei. At the level of the facial inner genu, it turns medially to meet the facial nerve root, giving off the terminal fibers to the facial motor nucleus and to the raphe nuclei and to the opposite nuclei bilaterally. The HRP-labeled descending root takes the course caudally at least down to the C3 segment of the spinal cord, giving off the terminal fibers to the spinal tract nucleus, the nuclei of the IXth, Xth and XIIth cranial nerves and the pontine-medullary reticular formation. In the spinal cord, it descends bilaterally through the posterior fascicles, giving off the terminal fibers to the dorsal and ventral horns.
Kubota
K
K
Section of Anatomy, Tokyo Medical and Dental University, Japan.
Narita
N
N
Ohkubo
K
K
Hosaka
K
K
Nagae
K
K
Lee
M S
MS
Kawamoto
T
T
Kubota
M
M
Odagiri
N
N
D000344:Afferent Pathways; D000818:Animals; D001369:Axons / Q000648:ultrastructure; D007312:Eulipotyphla / Q000033:anatomy & histology*; D005260:Female; D006735:Horseradish Peroxidase; D008406:Masseter Muscle / Q000294:innervation*; D008410:Masticatory Muscles / Q000294:innervation*; D008465:Mechanoreceptors / Q000033:anatomy & histology*; D051379:Mice; D008813:Mice, Inbred ICR / Q000033:anatomy & histology*; D008856:Microscopy, Fluorescence; D008971:Moles / Q000033:anatomy & histology*; D009666:Nose / Q000294:innervation*; D011434:Proprioception; D014278:Trigeminal Nuclei / Q000033:anatomy & histology
D006735:Horseradish Peroxidase