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PubMed1986

[Effect of the destruction of the oral and caudal trigeminal nuclei on pain sensitivity in cats].

Structural changes of nociceptive response after separate lesions of the oral and caudal trigeminal nuclei were studied in chronic experiments on adult cats. The lesion of the oral nucleus was shown to increase pain response and that of the caudal nucleus--to cause its inhibition. A relationship between the specific and non-specific projection systems of the brain in the development of pain is discussed.

Animals↗

PubMed1980

Ascending projections from the lateral descending and common sensory trigeminal nuclei in python.

The primary sensory trigeminal system of Python is characterized by the presence of an additional nucleus which is involved in processing data obtained by infrared sensors. This so-called lateral descending nucleus (LTTD) is strictly separated from the nuclei of the common sensory trigeminal system. The present study was undertaken in order to establish the relation between the two sensory trigeminal systems and higher brainstem structures. Further we studied whether the projections of these two systems remain separated at higher brainstem levels. It is shown that the organization of particularly the thalamus is characterized by the presence of specific projection areas of each of the two trigeminal systems: a) the ability of infrared preception is reflected particularly in the presence of an unique thalamic nucleus: the nucleus pararotundus and probably also in the enlargement of nucleus rotundus; and b) distinct subnuclei in the thalamic ventral nuclear complex are related to the various nuclei of the common sensory trigeminal system. The main ascending projection of LTTD runs via a distinct tract to the central gray layer (SGC) of the contralateral tectum mesencephali and the nucleus pararotundus (PR). Rostrally, numerous fibres decussate again via the tectal commissure and terminate ipsilaterally in the rostral part of SGC and in PR. The ascending projections of the common sensory trigeminal nuclei resemble those of mammals by gaining thalamic nuclei (ventral nuclear complex). No projections of the tectum nor to the striatum (like in birds) were observed. The two sensory trigeminal systems remain separately organised, in their projections as well as in their structure. No major connection between the two trigeminal system is present.

Animals↗

PubMed1992

Excitatory amino acid binding sites in the trigeminal principal sensory and spinal trigeminal nuclei of the rat.

Quantitative autoradiography was used to examine the density and distribution of excitatory amino acid (EAA) binding site subtypes in the principal sensory and spinal trigeminal nuclei of the rat trigeminal complex. The highest densities of N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), kainate and metabotropic receptors were found in the superficial laminae (I and II) of subnucleus caudalis, a region known to be densely innervated by primary afferent nociceptive terminals. Lower densities of EAA binding sites were observed in spinal subnuclei interpolaris and oralis and within the principal sensory nucleus. These results are consistent with the hypothesis that EAAs are involved in primary afferent nociceptive neurotransmission.

Animals↗

PubMed1985

[Effect of electroacupuncture and morphine on evoked potentials in the oral and caudal trigeminal nuclei in the cat].

Electroacupuncture effects on the functions of the oral and caudal trigeminal nuclei were comparatively analyzed in acute experiments on cats narcotized by hexinal (50 mg/kg). Responses evoked in the caudal nucleus by tooth pulp stimulation were inhibited while responses to mouth mucosa stimulation remained unchanged. In the oral nucleus responses to both types of stimulation were relieved. The same results were obtained in an experiment with systemic injection of morphine (5 mg/kg). It is suggested that different parts of the caudal nucleus are responsible for the transmission of discriminative and diffuse components of the nociceptive signals to the specific and nonspecific projection systems. The oral nucleus may be involved in the transmission of signals about mouth lesions conveying the necessity for defense reactions.

Acupuncture Therapy↗

PubMed1986

Pathway of the blink reflex in the brainstem of the cat: interneurons between the trigeminal nuclei and the facial nucleus.

Blink reflex responses evoked by electrical stimulation of the supraorbital nerve were examined using cats and the pathway of the blink reflex in the brainstem was elucidated. Both early response (ER) and late response (LR) were mediated by the main sensory trigeminal nucleus and the spinal trigeminal nucleus. However, a lesion of the main sensory trigeminal nucleus had less effect on the blink reflex than a lesion of the spinal trigeminal nucleus. The ER was mediated not only by the shorter disynaptic pathway of 3 neurons through the trigeminal nerve, the trigeminal nuclei and the facial nucleus but also by a polysynaptic pathway of 4 neurons. The interneurons were located between the trigeminal nuclei and the facial nucleus. Some of these interneurons participated in the production of both ER and LR. The area of the brainstem responsible for ER and LR of the blink reflex was the reticular formation from the rostral part of the medulla to the pons except the medial area around the median sulcus. The LR interneurons were distributed more widely than the ER interneurons.

Animals↗

PubMed1986

The projection to the mesencephalon from the sensory trigeminal nuclei. An anatomical study in the cat.

The terminal areas and the cells of origin of the projection from the sensory trigeminal nuclei to the mesencephalon were investigated, using the method of anterograde and retrograde transport of horseradish peroxidase or wheat germ agglutinin-horseradish peroxidase conjugate. Injection of tracer into the nucleus interpolaris or nucleus oralis (in the latter cases with involvement of the nucleus principalis) resulted in dense anterograde labeling in the deep and intermediate gray layers of the contralateral superior colliculus, extending throughout the rostrocaudal extent of the colliculus with the exception of its caudalmost part, which was not labeled. Minor projections to the intercollicular nucleus, posterior pretectal nucleus and nucleus of Darkschewitsch were found. Injection of tracer into the nucleus caudalis yielded a completely different result; terminal labeling in the midbrain was now present only in the periaqueductal gray matter, in its rostral and middle parts. The retrograde labeling observed after injection of tracer into the midbrain terminal areas showed that the cells of origin were located mainly in the alaminar spinal trigeminal nucleus, and the highest density of labeled neurons was found in the rostral part (subnucleus y) of the nucleus oralis. The retrograde labeling in the nucleus principalis was very sparse and almost exclusively involved peripherally located neurons. In the nucleus caudalis the overwhelming majority of the retrogradely labeled neurons were situated in its marginal layer. The functional implications of the above observations are discussed in relation to the findings in previous studies of the projections from the dorsal column nuclei and spinal cord to the midbrain. The combined results suggest that the trigeminal projections to the superior colliculus may be involved in the mechanisms of orientational behavior. The observation that the projection to the periaqueductal gray matter originates in the marginal layer suggests that it transmits information related to noxious stimuli.

Afferent Pathways↗

PubMed1987

A convergent input from nasal receptors and the larynx to the rostral sensory trigeminal nuclei of the cat.

1. Extracellular recordings were made from ninety-one neurones in the vicinity of the rostral trigeminal nucleus in chloralose-anaesthetized cats. 2. Sixty-two neurones within this area were activated by electrical stimulation of the ipsilateral superior laryngeal nerve (s.l.n.). Only two of the twenty-one neurones tested had an additional input from the contralateral s.l.n. 3. Fifty of these sixty-two neurones were also activated synaptically by light mechanical stimulation of the ipsilateral nasal cavity and in the eight neurones tested electrical stimulation of the ipsilateral nostril evoked activity. All these neurones exhibited characteristics of postsynaptic responses to s.l.n. and nasal stimulation, showing a variable latency to onset to either stimulus, summation and facilitation of more than one stimulus. 4. None of those neurones receiving an s.l.n. input, or those with convergent inputs from the s.l.n. and nose, could be affected by mechanical stimulation of any part of the face. 5. The activity of a further twenty-nine neurones was also recorded within this same general region. Sixteen responded to movement of the whiskers, five to touching the skin of the lower jaw, two to touching the skin of the upper jaw, three to touch around the eyebrows and three to touching other parts of the face. None of these neurones were activated by s.l.n. stimulation. 6. The location of seventeen of these neurones showing a convergent s.l.n. and nasal input was determined histologically. They were closely grouped together in a region 3.5-4.5 mm rostral to obex in and around the main trigeminal sensory nucleus, dorsolateral to the retrofacial nucleus corresponding to the parvocellular division of the alaminar spinal trigeminal nucleus. 7. The lack of somatosensory input to those neurones receiving a convergent input from the nose and s.l.n. is discussed in relation to previous studies describing somatosensory-visceral convergence to neurones within trigeminal nuclei.

Anesthesia, General↗

PubMed1986

Tooth pulp evoked potentials in trigeminal nuclei and parabrachial region of the freely moving rat.

Twelve hooded rats with chronically implanted recording electrodes in the left ponto-mesencephalic trigeminal nuclei and parabrachial region and bipolar stimulating electrodes in the left upper incisor were investigated in different states of spontaneous behaviour. At all recording sites tooth pulp evoked potentials (TPEP) with the following main components were recorded: a small negative component with a peak time of N 2 ms, followed by a second negativity with the peak time of N 6 ms and a slow large positive-negative component with the peak time of N 28 ms. The corresponding positive peaks were: P 3 ms, P 13 ms, P 58 ms. In all rats we observed a great variability of TPEP components in different waking states. A maximal decrease of TPEPs was observed during strong grooming compared with relaxed wakefulness.

Animals↗

PubMed1994

Central terminations of low-threshold mechanoreceptive afferents in the trigeminal nuclei interpolaris and caudalis of the cat.

Previous studies indicate that vibrissa, nonvibrissa, guard hair, hairy skin, and periodontal ligament afferents give rise to morphologically distinct terminal arbors in the trigeminal nuclei principalis (Vp) and oralis (Vo) in the cat. The present study describes the extent to which morphological and functional relationships exist in the nuclei interpolaris (Vi) and caudalis (Vc). Twenty-two fibers were physiologically characterized and stained by intra-axonal HRP injection techniques. The fast adapting (FA) vibrissa (VF) afferents gave rise to compact and circumscribed arbors in Vi and Vc. These tended to be larger in Vc than in Vi. The slowly adapting (SA) vibrissa (VS) afferents in Vi and Vc had more widespread and larger arbors than those of the VF afferents. The VS arbors in Vc tended to be larger and less circular than those in Vi. Guard hair (GH) afferents gave rise to circumscribed arbors in both nuclei, but those in Vc tended to have larger and more circular arbors than those in Vi. Down hair (DH) afferents gave rise to small, circumscribed arbors or a few distinct patches of boutons within a small area in Vi; arbors in Vc were less extensive and "stringy." Unlike other afferents, DH arbors were larger in Vi than in Vc, but smaller than those of GH afferents in either nuclei. The SA hairy skin (SS) afferents had arbors that were widespread with a few distinct patches of boutons; the arbors in Vc were larger than those in Vi. The arbors of SS afferents were smaller than those of VS and GH afferents in both nuclei. Like GH afferents, FA periodontal ligament (PF) afferents gave rise to large and circumscribed arbors in Vi, although the arbors in Vc were smaller and less dense. The present study demonstrated significant functional and morphological relationships for primary afferents in Vi and Vc, thus suggesting that sensory information from each of the distinct fiber or functional classes is processed in a characteristic manner in the individual nuclei.

Afferent Pathways↗

PubMed2005

Neuron numbers in the sensory trigeminal nuclei of the rat: A GABA- and glycine-immunocytochemical and stereological analysis.

The volume, total neuron number, and number of GABA- and glycine-expressing neurons in the sensory trigeminal nuclei of the adult rat were estimated by stereological methods. The mean volume is 1.38+/-0.13 mm3 (mean+/-SD) for the principal nucleus (Vp), 1.59+/-0.06 for the n. oralis (Vo), 2.63+/-0.34 for the n. interpolaris (Vip), and 3.73+/-0.11 for the n. caudalis (Vc). The total neuron numbers are 31,900+/-2,200 (Vp), 21,100+/-3,300 (Vo), 61,600+/-8,300 (Vip), and 159,100+/-25,300 (Vc). Immunoreactive (-ir) neurons were classified as strongly stained or weakly stained, depending on qualitative criteria, cross-checked by a densitometric analysis. GABA-ir cells are most abundant in Vc, in an increasing rostrocaudal gradient within the nucleus. Lower densities are found in Vip and Vp. The mean total number of strongly labeled GABA-ir neurons ranges between 1,800 in Vp to 7,800 in Vip and 22,900 in Vc, and varies notably between subjects. Glycine-ir neurons are more numerous and display more homogeneous densities in all nuclei. Strongly labeled Gly-ir cells predominate in all nuclei, their total number ranging between 9,400 in Vp to 24,300 in Vip and 34,200 in Vc. A substantial fraction of immunolabeled neurons in all nuclei coexpress GABA and glycine. In general, all neurons strongly immunoreactive for GABA are small, while weakly GABA-ir cells which coexpress Gly are larger. In Vc, one-third of all neurons are immunoreactive: 16.6% of them are single-labeled for GABA and 31.6% are single-labeled for glycine. The remaining 51.8% express GABA and glycine in different combinations, with those showing strong double labeling accounting for 22.6%.

Animals↗

PubMed1984

Ultrastructure of transganglionic degeneration in brain stem trigeminal nuclei during normal primary tooth exfoliation and permanent tooth eruption in the cat.

Electron microscopy is used to study changes in the axons and terminals in the cat brain stem trigeminal nuclei, main sensory, and partes interpolaris and caudalis, during the process of natural tooth shedding. Areas previously showing light optical argyrophilic degeneration products and adjacent areas lacking this degeneration are included. Various types of alteration occur early during tooth loss, including increased presumed glycogen, increased cytoplasmic density, flocculence, lucency, and neurofilamentous hyperplasia. By the stage of maximum exfoliation, terminals and axons of marked density become prominent in areas showing argyrophilia, whereas nondense forms occur elsewhere. By late eruption ages, all forms of degenerated terminals and axons are rare, but phagocytes are heavily laden with similar forms of debris. The sequence of ultrastructural events is discussed in light of recent studies of transganglionic degeneration, their correlation with light microscopic findings, and the potential implications for central plasticity in this system.

Age Factors↗

PubMed1978

Projections to the inferior olive of the cat. II. Comparisons of input from the gracile, cuneate and the spinal trigeminal nuclei.

The present experiments compared the projections to the inferior olive of the cat from the gracile, cuneate and spinal trigeminal nuclei. A differential labeling strategy was used for these comparisons. It was found that all three somatic sensory nuclei project to portions of all three major divisions of the contralateral inferior olive. The spinal trigeminal n. may also project less densely to the ipsilateral medial accessory olive. Projections to the dorsal accessory nucleus (DAO) and the medially-adjacent ventral lamella of the principal nucleus are roughly somatotopically organized. Although there is considerable overlap between the projection zones, the gracile n. projects predominantly to lateral DAO, the cuneate n. projects predominantly to medial DAO, and the spinal trigeminal nucleus pars caudalis projects predominantly to the most medial portions of DAO and the ventral lamella of principal olive. Projections to the medial accessory olive, on the other hand, are not as highly organized. Instead, they overlap extensively within a small egg-shaped area in the middle of the caudal half of the nucleus. Whereas all portions of the gracile and cuneate nuclei project to the inferior olive, only the pars caudalis of the spinal trigeminal nucleus appears to do so. These results were compared with the three available olivocerebellar maps as well as with the available behavioral and electrophysiological evidence on cerebellar somatotopic organization. This comparison indicated that the inputs to the cerebellum from the three second-order somatosensory nuclei via the inferior olive appear to be generally consistent with cerebellar somatotopic organization. This consistency is apparent not only with respect to the longitudinally-organized, vermal and paravermal differences in the anterior lobe, but also with respect to the transversely-organized specific somatotopy of the intermediate zone of the anterior lobe and the paramedian lobule.

Animals↗

PubMed1985

[Modulating influence of the 2d somatosensory cortex of the cerebral cortex on the effects of electroacupuncture on the trigeminal nuclei].

The effect of reversible functional inactivation of the second somatosensory cortex of the cerebral hemispheres on changes in the transmission of the afferent signals in the trigeminal nuclei after electroacupuncture was studied in acute experiments on adult cats anesthetized with hexenal (59 mg/kg i. p.). After functional inactivation of the second somatosensory cortex electroacupuncture failed to facilitate the evoked potentials in the oral trigeminal nucleus by stimulation of the tooth pulp and the lip of the mouth. In the caudal nucleus, the inhibitory effect of electroacupuncture on noxious stimulation decreased. The involvement of this brain cortex in the mechanisms of action of electroacupuncture on functionally different nuclei is discussed.

Acupuncture Therapy↗

PubMed1988

Intraoral sensation in patients with brainstem lesions: role of the rostral spinal trigeminal nuclei in pons.

Two patients with caudal pontine lesions had diminished intraoral sensation for all modalities sparing facial sensation. A third patient with lateral medullary infarction developed diminished facial pain and temperature sensation sparing intraoral structures. This segregation of intraoral sensation within the brainstem is consistent with animal studies which show that the rostral spinal trigeminal nuclei in the caudal half of the pons play an important role in intraoral and dental sensation.

Adult↗

PubMed1988

Different sensitivity to hypoxia in neuronal activities of lateral vestibular and spinal trigeminal nuclei.

Electrophysiologic studies were performed to examine the effects of hypoxia on neuronal activities of the lateral vestibular and spinal trigeminal nuclei using rats anesthetized with chloral hydrate. The rats inhaled a gas mixture of 5% oxygen and 95% nitrogen for 3.5 minutes to induce hypoxia, followed by room air. Under these conditions, mean PaO2 was decreased from 85 to 22 mm Hg 3 minutes after the start of the inhalation concomitant with a decrease in blood pressure from 108 to 55 mm Hg. There were no significant differences in these variables between rats used for vestibular nucleus experiments and rats used for trigeminal nucleus experiments. In the lateral vestibular nucleus, hypoxia inhibited postsynaptic components of the evoked field potential, spike generation of monosynaptic neurons on vestibular nerve stimulation, and firing induced by iontophoretic application of glutamate. In the spinal trigeminal nucleus, however, there were no alterations of the field potential or spike generation of the neurons on trigeminal nerve stimulation. These results indicate that the lateral vestibular nucleus neurons are much more sensitive to hypoxia than the spinal trigeminal nucleus neurons. The failure of transmission in the monosynaptic neurons of the lateral vestibular nucleus is suggested to be due to the inhibition of excitability of the postsynaptic membrane.

Acetylcholine↗

PubMed1993

Representation of the body surface in the gracile, cuneate, and spinal trigeminal nuclei of the little red flying fox (Pteropus scapulatus).

The body surface representation in the gracile, cuneate, and spinal trigeminal nuclei of the little red flying fox (Pteropus scapulatus) was examined. As in other species, it was found that any single cross-section through all three nuclei contains a representation of most, or all, of the body surface. In the little red flying fox, however, this representation is arranged as a series of dorsolateral to ventromedially oriented bands, within which there are no apparent topographies. These bands are arranged in such a way that the spatial relationships between body regions in the representation do not reflect those at the periphery.

Animals↗

PubMed1996

Efferents from the lateral frontal cortex to spinomedullary target areas, trigeminal nuclei, and spinally projecting brainstem regions in the hedgehog tenrec.

This study was done in the Madagascan lesser hedgehog tenrec, an insectivore with a very poorly differentiated neocortex. The cortical region, known to give rise to spinal projections, was injected with tracer, and the cortical efferents to brainstem and spinal cord were analyzed. Bulbar reticular fields, in addition, were identified according to their cells of origin and the laterality of their spinal projections after injection of tracer. Only few cortical fibers could be traced from the bulbar pyramid into the ipsilateral spinal cord, particularly to the lateral funiculus. The projections to the dorsal column nuclei and the classical spinally projecting brainstem regions were also weak. Faint projections were demonstrated to the nucleus of the posterior commissure and the nucleus of Darkschewitsch. In comparison to other mammals, there was no evidence that the contralateral cortico-bulbo-spinal pathway was strengthened, substituting for the almost non-existent contralateral corticospinal projection. Unlike the sensorimotor apparatus controlling limb and body movements, the brainstem regions controlling the head and neck received prominent cortical projections. Direct corticotrigeminal projections and indirect pathways were well represented. The projections to the trigeminal nuclei and the lateral reticular fields were clearly bilateral; those to the superior colliculus were predominantly ipsilateral. The corticobulbar fibers left the pyramid along its entire extent; the principal trigeminal nucleus and the dorsolateral pontine tegmentum were supplied by additional fibers of the corticotegmental tract. The lateral frontal cortex also projected densely to the dorsolateral hypothalamus, the periaqueductal gray, and the adjacent mesencephalic tegmentum, components of the emotional motor system.

Animals↗

PubMed1992

The distribution of binding by isolectin I-B4 from Griffonia simplicifolia in the trigeminal ganglion and brainstem trigeminal nuclei in the rat.

The distribution of binding by the isolectin I-B4 from Griffonia simplicifolia in the rat trigeminal system has been investigated. This lectin binds to a sub-population of small-diameter trigeminal ganglion neurons. Double-labelling studies revealed that this lectin bound to all the trigeminal ganglion neurons containing somatostatin, whereas it bound to less than 25% of those containing calcitonin gene-related peptide or substance P. In the brainstem this lectin gave terminal-like staining in only the sub-nucleus caudalis of the trigeminal nuclei. In this nucleus, staining was most dense in the inner part of lamina II. Morphometric studies suggest that this lectin and that from the soybean recognize the same population of cells. The relationship of this data to those obtained in other studies using markers binding to glycoconjugates with a terminal alpha-galactose is discussed.

Animals↗