Experimental and histological study of the mesencephalic nucleus of the fifth cranial nerve and its relation to the muscles of mastication in the rat

Rakhawy, M.T.; Shehata, Samir; Badawy, Zaizafon

doi:10.1159/000143789

Cited by 10 publications

(3 citation statements)

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“…The total neuron counts for the trigeminal mesencephalic nucleus (Mes V) in the cat vary between 511 and 637 (SIVANANDASINGHAM and WARWICK, 1976). In the rat Mes V, approximately 52 % of the neurons are thought to be connected with the proprioceptors in the masticatory muscles (RAKHAWY et al, 1972). However, 7 % of these neurons are connected with contralateral muscles of mastication while the remaining 45 % are connected with ipsilateral muscles.…”

Section: Discussionmentioning

confidence: 99%

Diameter spectra of sensory and motor fibers in nerves to jaw-closing and jaw-opening muscles in the cat.

1982

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The masseter and the mylohyoid nerves were examined using electron microscopy after unilateral destruction of the trigeminal motor nucleus by kainic acid injection in order to evaluate the distribution of sensory and motor fibers in masticatory muscle nerves. The surviving axons were counted and their diameters measured, and the results were compared with data for control nerves. The diameters of the control masseter nerve fibers were bimodally distributed with peaks at 2-5 and 7-9 ƒÊm. The nerve fiber diameters on the injected side, i.e., afferent fibers, also showed a bimodal distribution with peaks at 2-4 and 6-9 ,um.

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Section: Discussionmentioning

confidence: 99%

Diameter spectra of sensory and motor fibers in nerves to jaw-closing and jaw-opening muscles in the cat.

1982

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“…This nucleus contains the cell bodies of two types of neurons, i.e., primary muscle-spindle afferents of ipsilateral jaw-closing muscles and mechanoreceptor afferents of ipsilateral maxillary and mandibular teeth (reviewed in Lund, 1991). The caudal part of the mesencephalic trigeminal nucleus holds 60% of the nucleus cells (Rakhawy et al, 1972). Afferent units responding to gentle surface pressure applied with a rod to different areas of the masseter, but not to pushing of the teeth with the mandible fixed, were identified as masseter muscle spindle afferents.…”

Section: Stimulation and Recordingmentioning

confidence: 99%

Functional Adaptability of Jaw-muscle Spindles after Bite-raising

et al. 2006

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In a previous experiment, we found that masseter muscle spindles show functional plasticity after 5 to 15 days under increased occlusal vertical dimension (iOVD). In the present study, we hypothesized that spindle function would eventually recover if longer observation periods were allowed. Therefore, in this study we investigated changes in masseter muscle spindle function over periods of 1 day to 8 weeks. Masseter muscle-spindle responses to ramp-and-hold jaw stretches were recorded from the mesencephalic trigeminal nucleus in 35 barbiturate-anesthetized female Wistar rats. The rats were previously divided into Control and iOVD groups, and those in the iOVD group received a 2.0-mm composite resin build-up to the maxillary molars. In this condition, there were no statistically significant differences in masseter muscle spindle sensitivity between Control and iOVD in the six- and eight-week subgroups. Our results further indicate a high degree of adaptability in masseter muscle spindle function following changes in OVD.

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“…The somata of most trigeminal afferent fibers lie in the 5Gn, except for afferents from muscle spindles of masticatory muscles and half the periodontal mechanoreceptors, which have their somata in the Me5 (Cody et al, 1972). Afferents from periodontal mechanoreceptors are present only in the caudal, triangular part of the nucleus (Minkels et al, 1991), where 60% of the Me5 cells are located (Rakhawy et al, 1972). In this study, we stimulated the 5Gn and the Me5 and compared the motor unit activities of the dorsal neck splenius muscles.…”

Section: Discussionmentioning

confidence: 96%

Nature of Neck Motor Unit Activities Evoked by Different Trigeminal Inputs in Rats

2003

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Recent reports have suggested functional interactions between the masticatory and head motor systems. However, the neurophysiological mechanisms behind these phenomena have not been thoroughly investigated. In this study, the motor unit activity was recorded bilaterally from the dorsal neck splenius muscles (SPL) while the cell bodies of trigeminal afferent fibers were stimulated at either the trigeminal mesencephalic nucleus (Me5) or the Gasserian ganglion (5Gn) in 13 barbiturate-anesthetized Wistar rats. After Me5 electrical stimulation, SPL motor unit responses were recorded ipsilaterally (n = 24), with an onset latency distribution between 1.3 and 1.8 ms. After 5Gn stimulation, SPL responses were recorded bilaterally from 18 single units, with latencies ranging from 2.2 to 2.4 ms. Our results suggest that there are at least two distinct pathways from the trigeminal afferents to the neck muscles, with significant functional differences.

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Experimental and histological study of the mesencephalic nucleus of the fifth cranial nerve and its relation to the muscles of mastication in the rat

Cited by 10 publications

References 1 publication

Diameter spectra of sensory and motor fibers in nerves to jaw-closing and jaw-opening muscles in the cat.

Diameter spectra of sensory and motor fibers in nerves to jaw-closing and jaw-opening muscles in the cat.

Functional Adaptability of Jaw-muscle Spindles after Bite-raising

Nature of Neck Motor Unit Activities Evoked by Different Trigeminal Inputs in Rats

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