Peripheral and central distribution of fibres of the mesencephalic trigeminal root in the rat

doi:10.1016/0304-3940(81)90198-1

Neuroscience Letters

Volume 27, Issue 1, 18 November 1981, Pages 13-17

https://doi.org/10.1016/0304-3940(81)90198-1 Get rights and content

Abstract

Using the cobalt labelling technique in the rat, mesencephalic afferent fibres were shown in all three divisions of the trigeminal nerve. The descending branches of mesencephalic trigeminal neurones extend to the 3rd cervical segment of the spinal cord. Collaterals of this tract terminate in the following structures: the supratrigeminal nucleus, the motor nuclei of V, VII and XII cranial nerves, the reticular formation, a distinct nucleus in the reticular formation and the solitary nucleus.

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Cited by (81)

Revisiting the supratrigeminal nucleus in the rat
2016, Neuroscience
The supratrigeminal nucleus (Vsup), originally proposed as a premotoneuron pool in the trigeminal reflex arc, is a key structure of jaw movement control. Surprisingly, however, the location of the rat Vsup has not precisely been defined. In light of our previous cat studies, we made two hypotheses regarding the rat Vsup: (1) the Vsup is cytoarchitectonically distinguishable from its surrounding structures; (2) the Vsup receives central axon terminals of the trigeminal mesencephalic nucleus (Vmes) neurons which are primary afferents innervating muscle spindles of jaw-closing muscles and periodontal ligaments around the teeth. To test the first hypothesis, we examined the cytoarchitecture of the rat Vsup. The Vsup was identified as an area medially adjacent to the dorsomedial part of trigeminal principal sensory nucleus (Vp), and extended from the level just rostral to the caudal two-thirds of the trigeminal motor nucleus (Vmo) to the level approximately 150 μm caudal to the Vmo. Our rat Vsup was much smaller and its location was considerably different in comparison to the Vsup reported previously. To evaluate the second hypothesis, we tested the distribution patterns of Vmes primary afferent terminals in the cytoarchitectonically identified Vsup. After transganglionic tracer applications to the masseter, deep temporal, and medial pterygoid nerves, a large number of axon terminals were observed in all parts of Vsup (especially in its medial part). After applications to the inferior alveolar, infraorbital, and lingual nerves, a small number of axon terminals were labeled in the caudolateral Vsup. The Vsup could also be identified electrophysiologically. After electrical stimulation of the masseter nerve, evoked potentials with slow negative component were isolated only in the Vsup. The present findings suggest that the rat Vsup can be cytoarchitectonically and electrophysiologically identified, receives somatotopic termination of the trigeminal primary afferents, and principally receives strong termination of the spindle Vmes primary afferents.
Direct projection from the lateral habenula to the trigeminal mesencephalic nucleus in rats
2016, Brain Research
Citation Excerpt :
Trigeminal mesencephalic nucleus (Vmes) neurons are primary afferents innervating the muscle spindles of jaw-closing muscles or the periodontal mechanoreceptors around teeth (Byers et al., 1986; Corbin and Harrison, 1940; Jerge, 1963; Luo et al., 1991; Matesz, 1981), and are, thus, homologous to the ganglion neurons whose cell bodies are located in the dorsal root ganglion or trigeminal ganglion.
Trigeminal mesencephalic nucleus (Vmes) neurons are primary afferents conveying deep sensation from the masticatory muscle spindles or the periodontal mechanoreceptors, and are crucial for controlling jaw movements. Their cell bodies exist in the brain and receive descending commands from a variety of cortical and subcortical structures involved in limbic (emotional) systems. However, it remains unclear how the lateral habenula (LHb), a center of negative emotions (e.g., pain, stress and anxiety), can influence the control of jaw movements. To address this issue, we examined whether and how the LHb directly projects to the Vmes by means of neuronal tract tracing techniques in rats. After injections of a retrograde tracer Fluorogold in the rostral and caudal Vmes, a number of neurons were labeled in the lateral division of LHb (LHbl) bilaterally, whereas a few neurons were labeled in the medial division of LHb (LHbm) bilaterally. After injections of an anterograde tracer, biotinylated dextranamine (BDA) in the LHbl, a small number of labeled axons were distributed bilaterally in the rostral and caudal levels of Vmes, where some labeled axonal boutons contacted the cell body of rostral and caudal levels of Vmes neurons bilaterally. After the BDA injection into the LHbm, however, no axons were labeled bilaterally in the rostral and caudal levels of Vmes. Therefore, the present study for the first time demonstrated the direct projection from the LHbl to the Vmes and the detailed projection patterns, suggesting that jaw movements are modulated by negative emotions that are signaled by LHbl neurons.
Oromotor Nuclei
2015, The Rat Nervous System: Fourth Edition
Muscles of the face, tongue and jaws are innervated by motoneurons in the lower brainstem. In most instances, the locations of motoneurons innervating specific muscles have been well characterized. Most of the projections to the oromotor nuclei originate from the brainstem, although in a few instances, cortical and hypothalamic projections have also been identified. Brainstem pathways include projections from orosensory structures (e.g., the trigeminal sensory complex), the nucleus of the solitary tract and the parabrachial nuclei, as well as noradrenergic and serotonergic input from raphe and catecholaminergic nuclei. In addition, midbrain projections to specific subdivisions of the facial nucleus mediate vibrissae, orbital and pinna movements. A large proportion of the projections to the oromotor nuclei, however are from specific regions of the brainstem reticular formation, within which are neurons with projections to multiple oromotor nuclei. These reticular formation structures are integral to the ororhythmic responses of mastication, licking, swallowing, respiration, and whisking.
Involvement of trigeminal mesencephalic nucleus in kinetic encoding of whisker movements
2014, Brain Research Bulletin
In previous experiments performed on anaesthetised rats, we demonstrated that whisking neurons responsive to spontaneous movement of the macrovibrissae are located within the trigeminal mesencephalic nucleus (Me5) and that retrograde tracers injected into the mystacial pad of the rat muzzle extensively labelled a number of Me5 neurons. In order to evaluate the electrophysiological characteristics of the Me5–whisker pad neural connection, the present study analysed the Me5 neurons responses to artificial whisking induced by electrical stimulation of the peripheral stump of the facial nerve. Furthermore, an anterograde tracer was injected into the Me5 to identify and localise the peripheral terminals of these neurons in the mystacial structures. The electrophysiological data demonstrated that artificial whisking induced Me5 evoked potentials as well as single and multiunit Me5 neurons responses consistent with a direct connection. Furthermore, the neuroanatomical findings showed that the peripheral terminals of the Me5 stained neurons established direct connections with the upper part of the macrovibrissae, at the conical body level, with fibres spiralling around the circumference of the vibrissae shaft. As for the functional role of this sensory innervation, we speculated that the Me5 neurons are possibly involved in encoding and relaying proprioceptive information related to vibrissae movements to other CNS structures.
Jaw muscle spindle afferents coordinate multiple orofacial motoneurons via common premotor neurons in rats: An electrophysiological and anatomical study
2012, Brain Research
Citation Excerpt :
Vme neurons also project centrally to broad areas in the brain stem (Mizuno and Sauerland, 1970; Matesz, 1981; Arvidsson and Raappana, 1989; Shigenaga et al., 1990; Luo et al., 1991; 1995; Zhang et al., 1991). Vme central axons are distributed rostral–caudally in the Vsup, the dorsal Vmo, parvocellular reticular nucleus (PCRt) alpha division (PCRtA), dorsolateral PCRt, dorsal medullary reticular nucleus (MdD) and all adjacent dorsomedial areas of the spinal trigeminal nucleus (dm-Vsp) (Matesz, 1981; Arvidsson and Raappana, 1989; Zhang et al., 1991; Luo et al., 1995). However, functional roles that these caudal projections of the Vme might play are still largely unknown.
Jaw muscle spindle afferents (JMSA) in the mesencephalic trigeminal nucleus (Vme) project to the parvocellular reticular nucleus (PCRt) and dorsomedial spinal trigeminal nucleus (dm-Vsp). A number of premotor neurons that project to the trigeminal motor nucleus (Vmo), facial nucleus (VII) and hypoglossal nucleus (XII) are also located in the PCRt and dm-Vsp. In this study, we examined whether these premotor neurons serve as common relay pool for relaying JMSA to multiple orofacial motoneurons. JMSA inputs to the PCRt and dm-Vsp neurons were verified by recording extracellular responses to electrical stimulation of the caudal Vme or masseter nerve, mechanical stimulation of jaw muscles and jaw opening. After recording, biocytin in recording electrode was inotophorized into recording sites. Biocytin-Iabeled fibers traveled to the Vmo, VII, XII, and the nucleus ambiguus (Amb). Labeled boutons were seen in close apposition with Nissl-stained motoneurons in the Vmo, VII, XII and Amb. In addition, an anterograde tracer (biotinylated dextran amine) was iontophorized into the caudal Vme, and a retrograde tracer (Cholera toxin B subunit) was delivered into either the VII or Xll to identify VII and XII premotor neurons that receive JMSA input. Contacts between labeled Vme neuronal boutons and premotor neurons were observed in the PCRt and adjacent dm-Vsp. Confocal microscopic observations confirmed close contacts between Vme boutons and VII and XII premotor neurons. This study provides evidence that JMSA may coordinate activities of multiple orofacial motor nuclei, including Vmo, VII, XII and Amb in the brainstem via a common premotor neuron pool.
Corticofugal direct projections to primary afferent neurons in the trigeminal mesencephalic nucleus of rats
2010, Neuroscience
Little is known about projections from the cerebral cortex to the trigeminal mesencephalic nucleus (Vmes) which contains the cell bodies of primary sensory afferents innervating masticatory muscle spindles and periodontal ligaments of the teeth. To address this issue, we employed retrograde (Fluorogold, FG) and anterograde (biotinylated dextranamine, BDA) tracing techniques in the rat. After injections of FG into the Vmes, a large number of neurons were retrogradely labeled in the prefrontal cortex including the medial agranular cortex, anterior cingulate cortex, prelimbic cortex, infralimbic cortex, deep peduncular cortex and insular cortex; the labeling was bilateral, but with an ipsilateral predominance to the injection site. Almost no FG-labeled neurons were found in the somatic sensorimotor cortex. After BDA injections into the prefrontal cortex, anterogradely labeled axon fibers and boutons were distributed bilaterally in a topographic pattern within the Vmes, but with an ipsilateral predominance to the injection site. The rostral Vmes received more preferential projections from the medial agranular cortex, while the deep peduncular cortex and insular cortex projected more preferentially to the caudal Vmes. Several BDA-labeled axonal boutons made close associations (possible synaptic contacts) with the cell bodies of Vmes neurons. The present results have revealed the direct projections from the prefrontal cortex to the primary sensory neurons in the Vmes and their unique features, suggesting that deep sensory inputs conveyed by the Vmes neurons from masticatory muscle spindles and periodontal ligaments are regulated with specific biological significance in terms of the descending control by the cerebral cortex.

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Neuroscience Letters

Abstract

References (14)

Fibers of trigeminal mesencephalic neurons in the maxillary nerve of the rat

Neurosci. Lett.

On the central course of afferent fibers in the trigeminal, facial, glossopharyngeal and vagal nerves and their nuclei in the mouse

Acta physiol. scand.

Degenerated nerve fibers within trigeminal branches following trigeminal root cutting in some mammals

Sperimentale

Muscle spindles and other sensory endings in the extrinsic eye muscles, the physiology and anatomy of these receptors and their connexions with the brainstem

Brain

Observations on the periferal distribution of fibers arising in the mescencephalic nucleus of the fifth cranial nerve

J. comp. Neurol.

Function of mesencephalic root of fifth cranial nerve

J. Neurophysiol.

Projections of the optic tectum and the mesencephalic nucleus of the trigeminal nerve in the tegulizard (Tupinabis nigropunctatus)

Cell Tiss. Res.

Cited by (81)

Revisiting the supratrigeminal nucleus in the rat

Direct projection from the lateral habenula to the trigeminal mesencephalic nucleus in rats

Oromotor Nuclei

Involvement of trigeminal mesencephalic nucleus in kinetic encoding of whisker movements

Jaw muscle spindle afferents coordinate multiple orofacial motoneurons via common premotor neurons in rats: An electrophysiological and anatomical study

Corticofugal direct projections to primary afferent neurons in the trigeminal mesencephalic nucleus of rats