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At least 19 recordsLinked to original sources
PubMed1983

Brainstem projections to the normal and noradrenergically hyperinnervated trigeminal motor nucleus.

The noradrenergic innervation of the trigeminal motor nucleus of the rat can be increased severalfold by neonatal treatment with the neurotoxin, 6-hydroxydopamine. The brainstem projections to the nucleus were studied by injecting HRP into the nucleus of normal and noradrenergically hyperinnervated rats. In order to identify the source of the noradrenergic innervation, the fluorescent dye, True Blue, was used as a retrograde tracer in combination with the glyoxylic acid histofluorescence method for catecholamines. In both control and neonatally treated rats, the noradrenergic innervation of the motor nucleus was shown to arise from an ipsilateral group of cells located among the fibers of the lateral lemniscus just rostral to the motor nucleus. Our results confirmed the high degree of specificity of noradrenergic innervation, which arises exclusively from this lateral tegmental noradrenergic cell group. During the process of sprouting, this specificity is maintained since only those noradrenergic cells normally innervating the nucleus were retrogradely labeled in neonatally treated animals. Other noradrenergic projections which are also increased in these animals, such as the nearby locus ceruleus innervation of the main sensory trigeminal nucleus, do not spread to the motor trigeminal nucleus. HRP-labeled nonadrenergic cells were concentrated dorsally, with scattered cells surrounding the nucleus. A similar distribution was observed contralateral to the injection site. The mesencephalic trigeminal nucleus was labeled only ipsilateral to the injection. The motor nucleus also receives an extensive bilateral input from the pontine and medullary reticular formation. The medial reticular formation nuclei, including nucleus pontis caudalis, nucleus gigantocellularis, and nucleus reticularis ventralis contained large labeled cells, which were especially numerous in the retrotrigeminal area. Smaller, lateral reticular formation neurons were concentrated rostrally and ipsilaterally in the nucleus pontis lateralis. HRP retrograde labeling revealed no obvious change in the overall pattern of cells innervating the trigeminal motor nucleus following noradrenergic hyperinnervation.

Animals↗
PubMed1987

Projections from lateral reticular nucleus neurons to trigeminal motor nucleus revealed by antidromic activation in rabbits.

In anesthetized rabbits, electrophysiological experiments were conducted to determine if neurons of the lateral reticular nucleus that modified their activity during masticatory movements project directly into the trigeminal motor nucleus. Of the 125 neurons tested, 50 responded to stimulation of the trigeminal motor nucleus; of these, 22 were antidromically excited. Among this last population, 9 were antidromically driven also by cerebellar stimulation. In these neurons the antidromic response evoked from one structure collided with the response antidromically evoked from the other, thus indicating that both potentials are from the same neuron projecting to the trigeminal motor nucleus and the cerebellum. The remaining 28 neurons responding to stimulation of the trigeminal motor nucleus were orthodromically activated with a wider range of latencies. The possible significance of these findings in the organization of the rhythmic masticatory movements is briefly discussed.

Action Potentials↗
PubMed2005

Colocalization of serotonin and substance P in the postnatal rat trigeminal motor nucleus and its surroundings.

Trigeminal motoneurons are involved in a variety of oral motor activities, including mastication and breathing, which must be adapted to postnatal environmental change. Serotonin has both an excitatory and an inhibitory effect on trigeminal motor function, whereas substance P has mainly an excitatory effect. In the present study, we measured the density of serotonin- and substance P-immunoreactive nerve terminals in the trigeminal motor nucleus and the area 300 microm surrounding it in rats from embryonic day 19 to postnatal day 70. The density of these terminals gradually increased from embryonic day 19 to postnatal day 7 and decreased thereafter. The density was greatest in the ventromedial subnucleus of the trigeminal motor nucleus at embryonic day 19 and postnatal day 0 and in the area 300 microm surrounding trigeminal motor nucleus at postnatal day 4 and older. Two-color fluorescence immunohistochemistry was used to identify nerve processes immunoreactive for both substance P and serotonin. Approximately, 90% of serotonergic terminals also contained substance P at all ages examined, which suggests that the physiological function of terminals in which these neurotransmitters are colocalized is similar throughout development.

Animals↗
PubMed1983

A light and electron microscopic study of premotor neurons for the trigeminal motor nucleus.

Premotor neurons sending their axons to the trigeminal motor nucleus were observed in the cat by light and electron microscopy after labeling the neurons retrogradely or anterogradely with horseradish peroxidase (HRP). After HRP injection into the trigeminal motor nucleus, retrogradely labeled neurons were seen most frequently in the parvocellular reticular formation bilaterally. Many labeled neurons were also seen contralaterally in the intermediate zone at the rostralmost levels of the cervical cord and its rostral extension into the caudalmost levels of the medulla oblongata. Additionally, some neurons were labeled ipsilaterally in the mesencephalic trigeminal nucleus, contralaterally in the main sensory trigeminal nucleus and the trigeminal motor nucleus, and bilaterally in the oral and interpolar subnuclei of the spinal trigeminal nucleus. Only a few labeled neurons were seen in the confines of the gigantocellular reticular formation. All labeled neurons were small or of medium size; no large neurons were labeled. After HRP injection into the regions around the trigeminal motor nucleus or the parvocellular reticular formation, axodendritic terminals containing HRP granules were found contralaterally within the trigeminal motor nucleus. Some of these labeled terminals were filled with round synaptic vesicles and others contained pleomorphic synaptic vesicles. The varied morphology of labeled axon terminals was considered to reflect the functional heterogeneity of the premotor neurons for the trigeminal motor nucleus.

Animals↗
PubMed1988

Neurotoxic effects of p-chloroamphetamine on the serotoninergic innervation of the trigeminal motor nucleus: a retrograde transport study.

The rat forebrain receives projections from both dorsal and median raphe nuclei. It has recently been shown that serotoninergic axons arising from the dorsal raphe nucleus, but not those from the median raphe nucleus, degenerate following systemic administration of p-chloroamphetamine (PCA). The present study was conducted to determine (i) whether the motor nucleus of the trigeminal nerve is innervated by overlapping projections from multiple serotonin cell groups and (ii) whether a particular subset of serotoninergic axon terminals in the trigeminal motor nucleus are sensitive to the neurotoxic effects of PCA. Retrograde transport was used in combination with immunofluorescence to identify the serotonin-positive cells that project to the trigeminal motor nucleus both in control rats and in rats previously treated with PCA. In untreated rats, an average of 95 retrogradely labeled serotonin-positive neurons were found in the dorsal raphe nucleus, 135 in the nucleus raphe obscurus, 132 in the nucleus raphe pallidus and 63 in the ventrolateral medulla. After treatment with PCA, there was a marked decrease (-77%) in the number of retrogradely labeled serotoninergic neurons in the dorsal raphe nucleus, whereas the number of labeled neurons was unchanged in the raphe obscurus and raphe pallidus. These results demonstrate that PCA selectively lesions serotonin axon terminals arising from the dorsal raphe nucleus, while sparing projections from the raphe obscurus and raphe pallidus to the trigeminal motor nucleus. This conclusion is in agreement with previous findings that in the forebrain only axons from the dorsal raphe are vulnerable to PCA. The data provide further evidence that serotoninergic axons originating in the dorsal raphe nucleus differ from other serotoninergic axons in their pharmacological properties and that the dorsal raphe may contain a functionally unique subset of serotonin neurons.

Amphetamines↗
PubMed1991

Retrogasserian rhizotomy causes expression of nerve growth factor receptor-immunoreactive protein in motoneurons within the adult feline trigeminal motor nucleus.

The effect of lesions on nerve growth factor receptor (NGFr) immunoreactivity (IR) in motoneurons within the mature feline trigeminal motor nucleus was investigated. Ten days following complete unilateral retrogasserian trigeminal rhizotomy including transection of the trigeminal motor root, motoneurons within the ipsilateral trigeminal motor nucleus showed NGFr-IR. In contrast, motoneurons within the contralateral trigeminal motor nucleus and within both trigeminal motor nuclei in unoperated control subjects did not show NGFr-IR. It is suggested that the appearance of NGFr-IR in motoneurons within the ipsilateral trigeminal motor nucleus after rhizotomy represents an attempts towards recovery and may be associated with the regrowth of its cut axons.

Animals↗
PubMed2006

Morphological and immunohistochemical characterization of interneurons within the rat trigeminal motor nucleus.

Three series of experiments were carried out to characterize interneurons located within the trigeminal motor nucleus of young rats aged 5-24 days. Cholera toxin injections were made bilaterally into the masseter and, sometimes, digastric muscles to label motoneurons. In the first set of experiments, thick slices were taken from the pontine brainstem and cholera toxin-positive and cholera toxin-negative neurons located inside the trigeminal motor nucleus were filled with biocytin through whole-cell recording patch electrodes. Positively identified motoneurons (cholera toxin+) of various shapes and sizes always had a thick, unbranched axon that entered the motor root following a tight zigzag course. Many cholera toxin-negative neurons were also classified as motoneurons after biocytin filling based on this particularity of their axon. These are probably either fusimotor motoneurons or motoneurons supplying other jaw muscles. The cholera toxin-negative neurons classified as interneurons differed markedly from motoneurons in that they had thin, usually branched axons that supplied the ipsilateral reticular region surrounding the trigeminal motor nucleus (peritrigeminal area), the main trigeminal sensory nucleus, the trigeminal mesencephalic nucleus, the medial reticular formation of both sides, and the contralateral medial peritrigeminal area. Most often, their dendrites were arranged in bipolar arbors that extended beyond the borders of the trigeminal motor nucleus into the peritrigeminal area. Immunohistochemistry against glutamate, GABA and glycine was used to further document the nature and distribution of putative interneurons. Immunoreactive neurons were uniformly distributed throughout the rostro-caudal extent of the trigeminal motor nucleus. Their concentration seemed greater toward the edges of the nucleus and they were scarce in the digastric motoneuron pool. Glutamate- outnumbered GABA- and glycine-immunoreactive neurons. There was no clear segregation between the three populations. In the final experiment, 1,1'-dioctadecyl-3,3,3',3'-tetra-methylindocarbocyanine perchlorate crystals were inserted into one trigeminal motor nucleus in thick slices and allowed to diffuse for several weeks. This procedure marked commissural fibers and interneurons in the contralateral trigeminal motor nucleus. Together these results conclusively support the existence of interneurons in the trigeminal motor nucleus.

Animals↗
PubMed1988

Morphological and functional properties of trigeminal nucleus oralis neurons projecting to the trigeminal motor nucleus of the cat.

Horseradish peroxidase (HRP) was injected into the somata located in the rostrodorsomedial part (Vo.r) of the trigeminal nucleus oralis; an axonal projection to the trigeminal motor nucleus (Vmo) was demonstrated in two Vo.r neurons. The two neurons differed in their morphological and functional properties. The first Vo.r neuron responded to stimulation of low-threshold mechanoreceptors and its stem axon gave off massive axon collaterals that issued terminal branches to the dorsolateral subdivision of Vmo, Vo.r, and the medial and lateral parts of the lower brainstem reticular formation. The second Vo.r neuron was activated by stimulation of the tooth pulp or lingual nerve at twice longer latency than that of the first neuron. This stem axon was divided into two main ascending and one descending branches, and one of the main ascending branches was further bifurcated into two branches. The main non-bifurcated ascending branch gave off 4 collaterals, two of which sent terminal branches into the dorsolateral subdivision of Vmo and others into the Vo.r and juxta-trigeminal regions. The somato-dendroarchitectonic differences were also described in the two Vo.r neurons stained.

Animals↗
PubMed1985

Cerebral cortical projections to the reticular regions around the trigeminal motor nucleus in the cat.

Cerebral cortical regions which send projection fibers to the reticular regions around the trigeminal motor nucleus were identified in the cat by the horseradish peroxidase (HRP) method. The reticular region around the trigeminal motor nucleus are known to contain many interneurons for masticatory motoneurons. After injections of HRP into the reticular regions around the trigeminal motor nucleus, HRP-labeled neuronal cell bodies in the cerebral cortex were found in layer V. They were distributed bilaterally in the orbitofrontal cortical regions, mainly in the rostral extension of the orbital gyrus close to the presylvian sulcus; more were located in the floor and lateral bank of the presylvian sulcus than in the crown of the orbital gyrus. After injections of HRP conjugated with wheat germ agglutinin (WGA-HRP) into these cortical regions, many labeled presumed axon terminals were distributed bilaterally in the reticular regions around the trigeminal motor nucleus; mainly in the region ventral to the trigeminal motor nucleus and in the intertrigeminal region between the main sensory trigeminal nucleus and the trigeminal motor nucleus. Terminal labeling in these regions was more prominent after WGA-HRP injection into the lateral bank of the presylvian sulcus than after WGA-HRP injection into the crown of the orbital gyrus. Thus, the present results indicate that the main part of the cortical region projecting directly to the reticular regions around the trigeminal motor nucleus in the cat is folded into the presylvian sulcus.

Animals↗
PubMed2003

The physiological and morphological characteristics of interneurons caudal to the trigeminal motor nucleus in rats.

In this study we have characterized the membrane properties and morphology of interneurons which lie between the caudal pole of the trigeminal motor nucleus and the rostral border of the facial motor nucleus. Previous studies suggest that many of these interneurons may participate in the genesis of rhythmical jaw movements. Saggital brainstem slices were taken from rats aged 5-8 days. Interneurons lying caudal to the trigeminal motor nucleus were visualized using near-infrared differential interference contrast (DIC) microscopy, and were recorded from using patch pipettes filled with a K-gluconate- and biocytin-based solution. The 127 neurons recorded could be categorized into three subtypes on the basis of their responses to injection of depolarizing current pulses, namely tonic firing (type I), burst firing (type II) and spike-adaptive (type III) neurons. Type I interneurons had a higher input resistance and a lower rheobase than type II neurons. All three neuron subtypes showed 'sag' of the voltage response to injection of large-amplitude hyperpolarizing current pulses, and, in addition, also showed rectification of the voltage response to injection of depolarizing current pulses, with type II neurons showing significantly greater rectification than type I neurons. The axonal arborizations were reconstructed for 44 of 63 neurons labelled with tracer. Neurons of each subtype were found to issue axon collaterals terminating in the brainstem nuclei, including the parvocellular reticular nucleus (PCRt), the trigeminal motor nucleus (Vmot), the supratrigeminal nucleus or the trigeminal mesencephalic nucleus. Twenty-five of the 43 neurons issued collaterals which terminated in the Vmot and the other brainstem nuclei. When viewed under 100x magnification, the collaterals of some interneurons were seen to give off varicosities and end-terminations which passed close to the somata of unidentified neurons in the trigeminal motor nucleus and in the area close to the interneuron soma itself. This suggests that the interneurons may make synaptic contacts both on motoneurons and also on nearby interneurons. These results provide data on the membrane properties of trigeminal interneurons and evidence for their synaptic connections both with nearby interneurons and also with motoneurons. Thus, the interneurons examined could play roles in the shaping, and possibly also in the generation, of rhythmical signals to trigeminal motoneurons.

Anesthetics, Local↗
PubMed1988

Amygdaloid pathway to the trigeminal motor nucleus via the pontine reticular formation in the rat.

The connections of the amygdala with the trigeminal motor nucleus were studied by light and electron microscopy. Horseradish peroxidase (HRP) experiments showed that the pontine reticular formation, ventromedial to the spinal trigeminal nucleus at the level rostral to the genu of the facial nerve, receives fibers from the central nucleus of the amygdala ipsilaterally and sends fibers to the trigeminal motor nucleus contralaterally. Electron microscopic observations were carried out on the pontine reticular formation after electrolytic lesions in the central nucleus of the amygdala and HRP injections into the contralateral trigeminal motor nucleus were made on the same animal. These experiments using the combined degeneration and HRP technique clearly demonstrated that degenerating amygdaloid fibers made synaptic contacts with retrogradely labeled neurons.

Amygdala↗
PubMed1990

Representation of the tensor veli palatini muscle in the trigeminal motor nucleus of the Japanese monkey (Macaca fuscata).

Distribution of motoneurons supplying the tensor veli palatini (TVP) muscle was examined in the Japanese monkey (Macaca fuscata) by the retrograde horseradish peroxidase (HRP) method. Neurons labeled with HRP which was injected into the tensor veli palatini muscle were seen in the ventromedial aspects of the dorsolateral division of the trigeminal motor nucleus, at all rostrocaudal levels of the trigeminal motor nucleus. The vast majority of these TVP motoneurons were distributed around the margin, especially the dorsal margin, of the cluster of motoneurons which innervate the lateral pterygoid muscle.

Animals↗
PubMed1980

Early development and migration of the trigeminal motor nucleus in the chick embryo.

The development of the trigeminal motor nucleus in the chick embryo was studied using autoradiographic, cell staining, fiber staining, and axonal transport techniques. It was found that this nucleus arises very early in neurogenesis, with the first cells produced at 48 hours of incubation (stage 12), peak cell production at 50--56 hours (stage 15), and neuroblast proliferation completed by 72 hours (stage 18). As has been described in mammalian embryos, the primordial trigeminal cells move from the ventricular layer to accumulate as part of the common medial column, and later migrate in a ventrolateral direction to form the definitive lateral motor nucleus. The first identifiable component of the trigeminal system is the semilunar ganglion, which flanks the neural tube at stage 12, and sends afferents into the metencephalon by stage 13. By stage 12-13, the medial column cells are first apparent, and at stage 14, a few of these medial column cells have moved to begin formation of a lateral nucleus. At this time, a thin motor root can be seen exiting the brainstem. During subsequent stages, migratory traffic from medial to lateral regions increases, with cells frequently moving in association with fiber processes in the marginal zone. These fibers are presumed to emanate from secondary sensory, reticular, and medial column neuroblasts. By day 5, the medial column is greatly depleted and by day 6--7, the definitive lateral motor nucleus is formed. Beginning at 5 days, the dorsal motor nucleus can be detected, with cells from the lateral nucleus appearing to stream in a dorsomedial direction for its formation. Injections of horseradish peroxidase (HRP) into the mandibular process of the first visceral arch resulted in retrograde labeling of lateral nucleus cells as early as 3.5 days of incubation. In addition, migrating cells, intermediate between medial column and lateral nucleus, were similarly labeled. These observations indicate that processes of the lateral nucleus cells and those of migrating cells are well into their peripheral field at this age, but we cannot conclude that neuromuscular affiliations have been established, due to the possibility of HRP diffusion and growth cone uptake.

Animals↗
PubMed2003

Excitatory effects of hypocretin-1 (orexin-A) in the trigeminal motor nucleus are reversed by NMDA antagonism.

Hypocretin-1 and -2 (Hcrt-1 and -2, also called orexin-A and -B) are newly identified neuropeptides synthesized by hypothalamic neurons. Defects in the Hcrt system underlie the sleep disorder narcolepsy, which is characterized by sleep fragmentation and the involuntary loss of muscle tone called cataplexy. Hcrt neurons project to multiple brain regions including cranial and spinal motor nuclei. In vitro studies suggest that Hcrt application can modulate presynaptic glutamate release. Together these observations suggest that Hcrt can affect motor output and that glutamatergic processes may be involved. We addressed these issues in decerebrate cats by applying Hcrt-1 and -2 into the trigeminal motor nucleus to determine whether these ligands alter masseter muscle activity and by pretreating the trigeminal motor nucleus with a N-methyl-d-aspartate (NMDA) antagonist to determine if glutamatergic pathways are involved in the transduction of the Hcrt signal. We found that Hcrt-1 and -2 microinjections into the trigeminal motor nucleus increased ipsilateral masseter muscle tone in a dose-dependent manner. We also found that Hcrt application into the hypoglossal motor nucleus increases genioglossus muscle activity. Pretreatment with a NMDA antagonist (d-(-)-2-amino-phosphonovaleric acid) abolished the excitatory response of the masseter muscle to Hcrt-1 application; however, pretreatment with methysergide, a serotonin antagonist had no effect. These studies are the first to demonstrate that Hcrt causes the excitation of motoneurons and that functional NMDA receptors are required for this response. We suggest that Hcrt regulates motor control processes and that this regulation is mediated by glutamate release in the trigeminal motor nucleus.

2-Amino-5-phosphonovalerate↗
PubMed1995

Premotor neurons for trigeminal motor nucleus neurons innervating the jaw-closing and jaw-opening muscles: differential distribution in the lower brainstem of the rat.

The distribution of premotor neurons for trigeminal motor nucleus neurons innervating the jaw-closing and jaw-opening muscles was examined in the lower brainstem of the rat by using retrograde and anterograde labeling techniques. First, Fluorogold, a fluorescent retrograde tracer, was injected into the dorsolateral or ventromedial division of the trigeminal motor nucleus, each of which contains motoneurons innervating the jaw-closing or jaw-opening muscles, respectively. Second, Phaseolus vulgaris-leucoagglutinin, an anterograde tracer, was injected into each of the lower brainstem sites, where clusters of retrogradely labeled premotor neurons had been seen in the first set of experiments. Third, after injection of the anterograde tracer into a lower brainstem site, followed by injection of the retrograde tracer cholera toxin B subunit into a masticatory muscle, termination of anterogradely labeled axons onto retrogradely labeled motoneurons was confirmed with the aid of a confocal laser-scanning microscope. It was found that the premotor neurons distributed in the mesencephalic trigeminal nucleus, medial part of the parabrachial region, supratrigeminal region, and dorsal parts of the principal sensory, oral spinal and interpolar spinal trigeminal nuclei project preferentially to the dorsolateral division of the trigeminal motor nucleus, whereas those in the lateral part of the parabrachial region, intermediate parts of the principal sensory, oral spinal and interpolar spinal trigeminal nuclei, and alpha part of the gigantocellular reticular nucleus project preferentially to the ventromedial division of the trigeminal motor nucleus. The dorsal and lateral parts of the medullary reticular formation and the medullary raphe nuclei contain premotor neurons of both types. Group k motoneurons, a cluster of trigeminal motoneurons that innervate the tensor tympani muscle, receive projection fibers predominantly from the dorsolateral part of the oral pontine reticular formation.

Animals↗