The distribution of afferent neurones in the mesencephalic nucleus of the fifth nerve in the cat

Abstract

The objective of this study was to examine anatomically the distribution of afferent neurones in the mesencephalic nucleus of the fifth nerve (Mes V). HRP was applied, in separate experiments, to the inferior alveolar, infraorbital, and masseter nerves, and injected into the masseter muscle and periodontal ligament. Following application of HRP to the masseter muscle and masseter nerve, labelled cells were found in the ipsilateral motor nucleus of the fifth nerve and in the ipsilateral Mes V. Labelled cells in Mes V, identified as belonging to proprioceptor afferents from jaw-closing muscles, were distributed throughout the full extent of the nucleus. Following application of HRP to the inferior alveolar nerve, infraorbital nerve, and periodontal ligament, labelled cells were found in the ipsilateral trigeminal ganglion and Mes V, and the latter identified as belonging to periodontal receptor afferents. In contrast to the distribution of spindle afferent somata, they were restricted to the caudal region of Mes V. The differential distribution of afferent neurones within Mes V demonstrated in this study confirms previous electrophysiological findings, and its significance is considered.

The role of periodontal receptors in the jaw‐opening reflex in the cat.

“…In using graded electrical stimulation it is essential to monitor the afferent volleys from the NV entry region. Stereotaxically placed tungsten semi-microelectrodes were very convenient for this purpose (Linden, 1978;Gottlieb, Taylor & Bosley, 1984) offers a way of specifically exciting a large proportion of them without involvement of intra-dental, cutaneous or gingival afferents, provided that mental nerve branches are monitored to ensure absence of stimulus spread to their central processes in the other nuclei of NV. Concurrent stimulation of afferents from jaw-closer muscle spindle afferents also in MesV causes no problems because it is well established that they exert no direct action on digastric motoneurones (Kidokoro etal.…”

Distribution of mesencephalic nucleus and trigeminal ganglion mechanoreceptors in the periodontal ligament of the cat.

“…However, it was not known whether the cell bodies of the mechanoreceptors were in either the mesencephalic nucleus or the trigeminal ganglion. Anatomical studies in the cat (Weill, Bensadoun & de Tourniel, 1975;Chiego, Bradley, Cox & Avery, 1979;Byers & Matthews, 1981;Gottlieb, Taylor & Bosley, 1984;Byers, O'Connor, Martin & Dong, 1986) have shown neurones to be present in the periodontal ligament which have their cell bodies in either the trigeminal ganglion or the mesencephalic nucleus. However, a clear understanding of the position and distribution of the receptors themselves has not yet emerged.…”

Interaction of Periodontal and Jaw Elevator Spindle Afferents in the Cerebellum – Sensory Calibration

“…However, this finding is quite in accord with ana tomical experiments in which chromatoly sis of MeV cells, when caused by cerebel lar lesions [Brodal and Saugstad, 1965], af fected only the caudal part of the nucleus. It is in this region that the first order cell bodies of periodontal afferents are known to be concentrated as mentioned in the In troduction and recently confirmed by HRP experiments [Gottlieb et al, 1984]. So far, the evidence that it is the periodontal afferents with their first order cell bodies in the MeV, which have the direct MF pro jection, is only circumstantial.…”