Os objetivos do presente trabalho foram: 1) analisar a distribuição das fibras nervosas autonômicas na articulação temporomandibular (ATM) do rato, através da detecção de tirosina hidroxilase (TH), neuropeptídeo Y (NPY) e peptídeo intestinal vasoativo (VIP); 2) realizar um estudo topográfico ultra-estrutural das fibras e terminações nervosas autonômicas na ATM do rato; 3) determinar o padrão de ativação neuronal no complexo nuclear trigeminal e, em centros nervosos moduladores da dor, durante a vigência de monoartrite no complexo articular temporomandibular (CATM) do rato. Para o primeiro propósito o método imunoistoquímico, para a detecção simultânea de TH, NPY e VIP, foi executado em ATMs que apresentavam as seguintes condições: inervação intacta ou desprovida de inervação simpática e/ou parassimpática. Para o segundo propósito aliamos o tratamento prévio com 5-hidroxidopamina, para evidenciação de terminações nervosas simpáticas, com a remoção cirúrgica do gânglio ótico, para a visualização das fibras e terminações nervosas parassimpáticas em degeneração, em seguida analisamos as ATMs ao microscópio eletrônico de transmissão. O terceiro propósito foi obtido induzindo-se monoartrite (fase aguda, crônica e crônica ativa) no CATM e, verificando a expressão de Fos, um marcador de ativação neuronal, no complexo nuclear sensorial trigeminal e nos principais centros nervosos moduladores da dor, situados no tronco encefálico (substância cinzenta periaqueductal- PAG; área rostral ventromedial da medula oblonga- RVM; locus coeruleus- LC; área caudal ventrolateral da medula oblonga- CVLM; núcleo do trato solitário- NTS e; núcleo reticular ventral-NRV). Verificamos que as ATMs desprovidas de inervação simpática apresentam exclusivamente uma pequena quantidade de fibras nervosas VIP-IR, ao passo que aquelas desprovidas de inervação parassimpática mostram uma grande quantidade de fibras nervosas TH/NPY-IR e TH/NPY/VIP-IR. As fibras e terminações nervosas autonômicas foram observadas em vasos sanguíneos ou isoladas no tecido conjuntivo, especialmente na membrana sinovial. No que se refere à expressão de Fos, constatamos que o subnúcleo caudal do núcleo do tracto espinal do nervo trigêmeo (Sp5C) e a PAG apresentaram um aumento bilateral significante na expressão de Fos durante todas as fases da monoartrite induzida no CATM. Todavia, RVM, LC, CVLM, NTS apresentaram uma quantidade de neurônios Fos-IR significativamente aumentada, de ambos os lados, apenas quando o CATM estava sob vigência de monoartrite na fase aguda e crônica ativa. Concluímos que: 1) a ATM mostra-se densamente inervada por fibras nervosas simpáticas (TH/NPY-IR e TH/NPY/VIP-IR) e, por uma discreta quantidade de fibras nervosas parassimpáticas (VIP-IR), ambas predominantemente associadas com vasos sanguíneos; 2) o Sp5C e a PAG, mostra-se intensamente ativados em todas as fases da monoartrite no CATM, ao passo que a maioria dos centros nervosos moduladores da dor apresentam uma quantidade aumentada de neurônios imunoarreativos ao marcador de ativação neuronal, Fos, apenas durante as fases aguda e crônica ativa dessa monoartrite. / The goals of the present study were: 1) to analyse the distribution of autonomic nerve fibers in the rat temporomandibular joint (TMJ) under normal conditions using immunofluorescence method to detect tirosyne hydroxylase (TH), neuropetide Y (NPY) and vasoactive intestinal polypeptide (VIP); 2) to verify the detailed distribution of autonomic nerve fibers in the rat temporomandibular joint by transmission electron microscopy; 3) to determine the neuronal activation pattern in the trigeminal system and in the pain modulation centers during monoarthritis induced in the rat temporomandibular joint complex (TMJC). For the first purpose, histologic sections from TMJs with intact innervation or with surgical sympatectomy and/or parasympathectomy were submitted to simultaneous detection of TH, NPY and VIP. For the second purpose, 5-hydroxidopamine treatment to detect sympathetic nerve endings was combined with surgical parasympatectomy of the otic ganglion to detect degenerated parasympathetic nerve endings in the rat TMJC, by transmission electron microscopy. For the last purpose, monoarthritis (acute, chronic and chronic-active phases) was induced in the TMJC and histologic sections from the brain stem were submitted to immunodetection of Fos protein in the trigeminal system and in the pain modulation centers (periqueductal gray matter - PAG; rostroventromedial medulla - RVM; locus coeruleus- LC; caudal ventrolateral medulla- CVLM; nucleus of the solitary tract - NTS; ventral reticular nucleus - VRN). The most important results demonstrated that the TMJC showed a discrete parasympathetic innervation (VIP-IR), while the sympathetic innervation was dense and characterized by TH-/NPY-/VIP-IR or TH-/NPY-IR nerve fibers. Autonomic nerve fibers were mainly noted associated to blood vessels and occasionally disperse in the synovial membrane. Fos-IR neurons showed significant bilateral increase in the spinal trigeminal caudal subnucleus and PAG during arthritis evolution. On the other hand, RVM, LC, CVLM and NTS only showed significant increase of Fos-IR neurons during the acute and chronic-active phases of monoarthritis. The main conclusions were: 1) the TMJC shows a dense sympathetic innervation (TH/NPY-IR or TH-/NPY-/VIP-IR) and discrete parasympathetic innervation (VIP-IR), both associated mainly to blood vessels; 2) most modulation pain centers are activated principally during acute and chronic-active arthritis, while the spinal trigeminal caudal subnucleus and PAG showed continuous activation during all phases of arthritis.

Le trouble de l’odorat est un symptôme fréquent bien connu de la Maladie de Parkinson (MP). Il apparaît plusieurs années avant la possibilité d’un diagnostic de la maladie et son étude est ainsi d’intérêt particulier pour aider au développement d’outils de dépistage précoces et la sélection de candidats pouvant participer à des essais cliniques visant le développement de traitements potentiellement curateurs. Pour ce faire, il est important de différencier un trouble de l’odorat associé à la MP d’autres troubles de l’odorat non reliés à une maladie neurodégénérative (trouble de l’odorat non-parkinsonien : TONP), tels que des troubles de l’odorat liés à une infection virale, à un traumatisme craniocérébral ou des troubles sinu-nasaux. Le système olfactif est plus complexe qu’il ne le semble et est intimement lié au système trigéminal, un système moins bien connu, qui permet, entre autres, la perception de sensations de fraicheur, chaleur et picotement des odeurs. L’interaction entre les systèmes olfactif et trigéminal est complexe et peu connue. La sensibilité trigéminale est typiquement réduite dans le cas d’un système olfactif altéré dans les TONP, mais il n’est pas bien compris comment les deux systèmes interagissent ensemble dans le cas d’un trouble de l’odorat associé à la MP. L’objectif principal de cette thèse visait donc la caractérisation du trouble de l’odorat associé à la MP lorsque spécifiquement comparé à des patients atteints de TONP. Par conséquent, cette thèse avait aussi pour objectif d’apporter une meilleure compréhension de l’interaction entre les systèmes olfactif et trigéminal dans le cas d’un système olfactif fonctionnel et d’un système olfactif altéré dans la MP et d’autres TONP. Nous avons donc d’abord évalué la sensibilité olfactive et trigéminale, sur le plan comportemental (étude 1). Cette première étude a permis d’identifier un patron de réponse spécifique dans la MP avec un système olfactif altéré et un système trigéminal intact,en comparaison à des contrôles, en contraste à une sensibilité trigéminale réduite dans les TONP. Dans le même ordre d’idée, nous avons ensuite évalué la perception des dimensions trigéminales et olfactives de différentes odeurs (étude 2). Nos résultats suggèrent que la perception de sensations trigéminales est intacte chez les patients avec la MP en contraste à la perception de dimensions olfactives qui est réduite, comparativement à des contrôles. Pour mieux comprendre l’interaction entre le système olfactif et trigéminal dans le cas d’un système olfactif fonctionnel, nous avons ensuite évalué l’impact d’un stimulus olfactif sur la capacité à latéraliser un stimulus trigéminal chez des participants contrôles (étude 3). Cette étude a démontré un effet d’amplification de la réponse trigéminale lors d’une co-stimulation olfactive ipsilatérale suggérant ainsi une interaction au niveau de l’épithélium nasal. Afin de mieux comprendre la réponse trigéminale dans la MP, nous avons évalué la sensibilité trigéminale périphérique et centrale en réponse à un stimulus trigéminal pur via des mesures électrophysiologiques (étude 4). Nous avons ainsi démontré une altération spécifique de la réponse trigéminale dans la MP comparativement à d’autres TONP et à des contrôles. Puisque le bulbe olfactif est l’une des premières régions affectées dans la MP, nous avons ensuite mesuré le volume du bulbe olfactif sur des images IRM (étude 5). Nos résultats ont démontré un volume réduit dans la MP et les TONP comparativement à des contrôles, mais aucune différence entre les patients atteints de la MP et de TONP. Néanmoins, l’utilisation de techniques d’apprentissage profond sur les images IRM du bulbe olfactif a permis de différencier les patients avec la MP des TONP avec une exactitude considérable. Enfin, nous avons étudié la connectivité fonctionnelle au sein du réseau chimiosensoriel (étude 6). Nous avons ainsi identifié des altérations spécifiques de la connectivité et la modularité des réseaux entre des régions de traitement olfactif et trigéminal au repos et lors de la réalisation d’une tâche olfactive et d’une tâche trigéminale chez des patients atteints de la MP en comparaison avec des TONP et des contrôles. En conclusion, la série d’études présentée dans cette thèse contribue à une meilleure compréhension du trouble de l’odorat associé à la MP et propose de potentielles pistes pour le différencier d’autres TONP, notamment par la mesure du système trigéminal. Cette thèse apporte une meilleure compréhension de l’interaction entre le système olfactif et trigéminal dans un système olfactif fonctionnel et de son altération dans les troubles olfactifs associés à la MP ou à d’autres TONP. La caractérisation de ce symptôme non-moteur pourra éventuellement aider au développement d’outils de dépistage précoce de la MP. / Olfactory dysfunction is a highly reliable non-motor symptom of Parkinson’s disease (PD) that appears several years before the possibility of a diagnosis of the disease. Hence, its study is of particular interest to help the development of early diagnosis tools and the selection of ideal candidates to participate in clinical trials that aims to test potential neuroprotective treatments. To do so, it is important to differentiate PD-related olfactory dysfunction from other non-neurodegenerative forms of olfactory dysfunctions that can be related to infections, head trauma or sinonasal disease (non-parkinsonian olfactory dysfunction: NPOD). The olfactory system is more complex than it seems and is intimately connected to the trigeminal system, a less well-known system, that allows, amongst others, the perception of sensation of freshness, warmth, and piquancy of odors. The interaction between the olfactory and trigeminal system is complex and not well understood. Trigeminal sensitivity is typically reduced in cases of an impaired olfactory system related to NPOD; however, this is not clear how both systems interact together in PD-related olfactory dysfunction. The main objective of this thesis was to principally characterize PD-related olfactory dysfunction when specifically compared to patients with NPOD. Consequently, this thesis also aimed to bring a better understanding of the interaction between the olfactory and trigeminal system in a fully functional olfactory system as well as in alterations of the olfactory system associated with PD and other NPOD. We have thus first assessed the olfactory and trigeminal sensitivity using behavioral measures (study 1). This study allowed the identification of a specific response pattern in PD patients with an altered olfactory system and an intact trigeminal system, when compared to controls, in contrast to the reduced trigeminal sensitivity observed in NPOD. We then evaluated the perception of trigeminal and olfactory dimensions of different odors (study 2). Our results suggest that the perception of trigeminal sensations is intact in patients with PD in contrast to the perception of olfactory dimensions which is reduced when compared to control participants. To better understand the interaction between the olfactory and trigeminal systems in a functioning olfactory system, we evaluated the impact of an olfactory stimulus on the capacity to lateralize a trigeminal stimulus in healthy participants (study 3). This study has demonstrated an amplification effect of the olfactory system on the trigeminal system particularly during ipsilateral co-stimulation, suggesting an interaction at the level of the olfactory mucosa. To better understand the trigeminal response in PD patients, we further investigated the peripheral and central trigeminal sensitivity in response to a pure trigeminal stimulus by means of electrophysiological measurements (study 4). We thus demonstrated a specific alteration of the trigeminal response in PD patients when specifically compared to patients with NPOD and healthy control participants. As the olfactory bulb is one of the first regions to be affected in PD, we then measured the olfactory bulb volume on MRI scans (study 5). Our results showed reduced olfactory bulb volume in PD patients as well as in NPOD, when compared to controls, but no difference between PD and NPOD patients. Interestingly, the use of deep learning techniques on MRI scans of the olfactory bulb allowed the discrimination between PD patients and NPOD patients with considerable accuracy. Finally, we investigated the functional connectivity within the chemosensory network (study 6). We identified a specific pattern of functional connectivity and chemosensory network modularity in PD patients at resting-state and while performing an olfactory or a trigeminal task, when specifically compared to patients with NPOD and controls. In conclusion, all taken together, the studies presented in this thesis contributes to a better understanding of the PD-related olfactory dysfunction and suggest potential avenues to differentiate it from NPOD, notably through the measurement of the trigeminal system. This thesis brings further knowledge regarding the interaction between the olfactory and trigeminal systems in a functional olfactory system and its alteration in cases of an impaired olfactory system related to PD or NPOD. The characterization of this non-motor symptom of the disease will eventually help the development of early diagnostic tools for PD.