Nociceptive Afferents to the Premotor Neurons That Send Axons Simultaneously to the Facial and Hypoglossal Motoneurons by Means of Axon Collaterals

It is well known that the brainstem premotor neurons of the facial nucleus and hypoglossal nucleus coordinate orofacial nociceptive reflex (ONR) responses. However, whether the brainstem PNs receive the nociceptive projection directly from the caudal spinal trigeminal nucleus is still kept unclear. Our present study focuses on the distribution of premotor neurons in the ONR pathways of rats and the collateral projection of the premotor neurons which are involved in the brainstem local pathways of the orofacial nociceptive reflexes of rat. Retrograde tracer Fluoro-gold (FG) or FG/tetramethylrhodamine-dextran amine (TMR-DA) were injected into the VII or/and XII, and anterograde tracer biotinylated dextran amine (BDA) was injected into the caudal spinal trigeminal nucleus (Vc). The tracing studies indicated that FG-labeled neurons receiving BDA-labeled fibers from the Vc were mainly distributed bilaterally in the parvicellular reticular formation (PCRt), dorsal and ventral medullary reticular formation (MdD, MdV), supratrigeminal nucleus (Vsup) and parabrachial nucleus (PBN) with an ipsilateral dominance. Some FG/TMR-DA double-labeled premotor neurons, which were observed bilaterally in the PCRt, MdD, dorsal part of the MdV, peri-motor nucleus regions, contacted with BDA-labeled axonal terminals and expressed c-fos protein-like immunoreactivity which induced by subcutaneous injection of formalin into the lip. After retrograde tracer wheat germ agglutinated horseradish peroxidase (WGA-HRP) was injected into VII or XII and BDA into Vc, electron microscopic study revealed that some BDA-labeled axonal terminals made mainly asymmetric synapses on the dendritic and somatic profiles of WGA-HRP-labeled premotor neurons. These data indicate that some premotor neurons could integrate the orofacial nociceptive input from the Vc and transfer these signals simultaneously to different brainstem motonuclei by axonal collaterals

Contribution à l'étude des interactions trigemino-gustatives périphériques et centrales (implication du nerf alvéolaire inférieur et du nerf lingual chez le rat)

Lors de la prise alimentaire, la détection et la transmission des signaux somesthésiques est assurée par le système trigéminal (V), notamment le nerf lingual (NL) destiné à la langue, et le nerf alvéolaire inférieur (NAI) responsable de l innervation des dents mandibulaires. La modalité gustative linguale est assurée par le nerf glossopharyngien (IX) et par une branche du nerf facial (VII), la corde du tympan (CT). Bien que distincts, les systèmes somesthésique et gustatif présentent de nombreuses interactions. Au cours de ce travail, nous nous sommes particulièrement intéressés aux interactions trigémino-gustatives périphériques et centrales chez le rat.Dans la première partie de ce travail, nous avons étudié l expression des transporteurs vésiculaires du glutamate (VGluts) dans les papilles gustatives linguales à l aide de techniques immuno-histochimiques. Nous avons tout d abord montré que seul VGlut 1, un marqueur du phénotype glutamatergique des neurones centraux, est présent dans les papilles gustatives linguales. Nous avons ensuite montré que certaines fibres de la CT et du NL expriment VGlut 1 dans les papilles fongiformes. Dans la deuxième partie de ce travail, nous nous sommes intéressés à la participation des neurones sensitifs primaires du NAI à la modulation du signal gustatif dans le noyau du tractus solitaire (NTS). A l aide d enregistrements électro-physiologiques unitaires, nous avons montré que les neurones du NAI modulent faiblement les réponses gustatives neuronales dans le NTS. Des techniques immuno-histochimiques ont ensuite permis de révéler la présence de projections des neurones du NAI sur des neurones gustatifs du NTS. Les données immuno-histologiques observées en périphérie indiquent la présence de fibres glutamatergiques de la CT et du NL dans les papilles fongiformes et suggèrent leur participation à la modulation périphérique du signal gustatif. Au niveau central, nos résultats précisent l implication des neurones du NAI, en particulier ceux qui innervent les dents mandibulaires, dans l intégration du signal gustatif.LILLE2-UFR Odontologie (593502202) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Trigemino-solitarii-facial pathway in rats

International audienceThis study was undertaken to identify premotor neurons in the nucleus tractus solitarii (NTS) serving as relay neurons between the sensory trigeminal complex (STC) and the facial motor nucleus in rats. Trigemino-solitarii connections were first investigated following injections of anterograde and/or retrograde (biotinylated dextran amine, biocytin, or gold-HRP) tracers in STC or NTS. Trigemino-solitarii neurons were abundant in the ventral and dorsal parts of the STC and of moderate density in its intermediate part. They project throughout the entire rostrocaudal extent of the NTS with a strong lateral preponderance. Solitarii-trigeminal neurons were observed mostly in the rostral and rostrolateral NTS. They mainly project to the ventral and dorsal parts of the spinal trigeminal nucleus but not to the principal nucleus. Additional neurons located in the middle NTS were found to project exclusively to the spinal trigeminal nucleus pars caudalis. No solitarii-trigeminal cells were observed in the caudal NTS. In addition, evidence was obtained of NTS retrogradely labeled neurons contacted by anterogradely labeled trigeminal terminals. Second, solitarii-facial projections were analyzed following injections of anterograde and retrograde tracers into the NTS and the facial nucleus, respectively. NTS neurons, except those of the rostrolateral part, reached the dorsal aspect of the facial nucleus. Finally, simultaneous injections of anterograde tracer in the STC and retrograde tracer in the facial nucleus gave retrogradely labeled neurons in the NTS receiving contacts from anterogradely labeled trigeminal boutons. Thus, the present data demonstrate for the first time the existence of a trigemino-solitarii-facial pathway. This could account for the involvement of the NTS in the control of orofacial motor behaviors

Facial cooling and peripheral chemoreflex mechanisms in humans

Reductions in arterial oxygen partial pressure activate the peripheral chemoreceptors which increase ventilation, and, after cessation of breathing, reduce heart rate. We tested the hypothesis that facial cooling facilitates these peripheral chemoreflex mechanisms.Journal ArticleResearch Support, Non-U.S. Gov'tFLWINinfo:eu-repo/semantics/publishe