Résumé : Introduction: À ce jour, notre compréhension des mécanismes neurophysiologiques responsables du développement d'une douleur chronique est encore relativement limitée. Il est proposé que certaines modifications dans l'efficacité des mécanismes endogènes d'inhibition descendante de la douleur pourraient contribuer à ce phénomène. Considérant l'importance de la neurotransmission monoaminergique dans les mécanismes descendants de modulation de la douleur, autant inhibiteur que facilitateur, nous émettons l'hypothèse que la persistance temporelle d'une douleur peut provoquer des modifications dans la fonctionnalité des deux systèmes majeurs (sérotoninergique et noradrénergique) sous-jacents à ces mécanismes de contrôle endogène, participant ainsi à la dynamique de développement et à la progression des états de douleur chronique à travers le temps. Objectif général: En utilisant une approche translationnelle, nous avons exploré l'association entre la fonctionnalité (centrale & périphérique) des systèmes de neurotransmission monoaminergique et l'efficacité des mécanismes descendants d’inhibition pendant le développement et la progression d'une douleur chronique. Résultats cliniques: D'une part, nos résultats répliquent plusieurs observations de la littérature ayant démontré une diminution de l'efficacité des mécanismes descendants d’inhibition de la douleur (à l'aide d'un paradigme de modulation conditionnée de la douleur; MCD) chez des sujets souffrant de douleur musculosquelettique chronique (sujets CP). Chez ces mêmes sujets, nous observons également une diminution des concentrations plasmatiques basales en noradrénaline (NA) et métanéphrine, lorsque comparés à des sujets sains (sujets PF). Pour tous les sujets testés (PF et CP), une association positive est mise en évidence entre l'efficacité de la MCD et les concentrations plasmatiques basales en NA et métanéphrine. Par conséquent, ces concentrations des catécholamines dans le plasma pourraient servir d'indicateurs moléculaires de l'efficacité latente de la MCD. Par ailleurs, aucune différence dans l'activité monoaminergique et aucune association avec l'efficacité de la MCD n'ont été observées au niveau du liquide céphalorachidien (LCR). Résultats précliniques: D'autre part, nous proposons un nouveau modèle de douleur à double atteinte chez le rongeur (i.e., induction initiale d'une douleur persistante [la 1ere atteinte] et activation subséquente des mécanismes descendants de modulation de la douleur à l'aide d'une douleur tonique [la 2e atteinte]). Ce paradigme expérimental nous permet ainsi d'évaluer l'efficacité des mécanismes descendants de modulation de la douleur chez les rongeurs en contexte de douleur chronique. Ainsi, nous mettons en évidence une diminution de la réponse comportementale à une douleur tonique (dans le test à la formaline), 28 jours après l'induction d'une douleur neuropathique (modèle de constriction chronique du nerf sciatique; CCI), lorsque comparés aux rats sham. Bien que cette diminution des comportements nociceptifs soit encore observable 168 jours après le début de la neuropathie, celle-ci semble tout de même s'amenuiser à travers le temps. Parallèlement, en l'absence de stimulation nociceptive tonique, une augmentation des concentrations en sérotonine et noradrénaline est observée au niveau central (i.e., dans le LCR) 12 jours après l'induction de la douleur neuropathique, avant de retourner ensuite à un niveau comparable à celui des rats sham au jour 28. Par ailleurs, la réponse comportementale observée au jour 28 est visible seulement dans un modèle de douleur neuropathique (CCI), et non lorsqu'une douleur inflammatoire est utilisée comme douleur persistante initiale. Conclusions: En contexte de douleur chronique, nos résultats chez l'humain confirment la présence de modifications dans l'efficacité des mécanismes descendants d’inhibition de la douleur, en plus de soutenir le concept émergent qui suggère que les différences dans l'efficacité de ceux-ci pourraient être associées à des différences individuelles dans certains processus périphériques (comme la relâche de catécholamines dans le sang), pouvant ultimement être impliquées dans la régulation cardiovasculaire. Par ailleurs, nos résultats chez le rongeur suggèrent que des changements dynamiques (spécifiques au type de douleur) dans l'efficacité des mécanismes descendants de modulation, ainsi que dans la fonctionnalité centrale des systèmes de neurotransmission monoaminergique, se produisent lors de la progression d'une douleur chronique. Dans son ensemble, cette thèse apporte de nouvelles informations au sujet des changements neurophysiologiques temporels au sein des mécanismes descendants de modulation de la douleur pouvant être impliqués dans le développement et la progression de la douleur chronique. / Abstract : Introduction: Hitherto, our understanding about the neurophysiological mechanisms responsible for the development of chronic pain is still relatively limited. It is suggested that modifications in the efficacy of endogenous pain inhibitory mechanisms could contribute to this phenomenon. Considering the importance of monoaminergic neurotransmission in descending pain modulation, either of inhibitory or facilitatory influence, we hypothesize that temporal persistence of pain can trigger modifications in the functionality of the two major systems (serotoninergic and noradrenergic) underlying these endogenous control mechanisms, thus participating in the development and progression of chronic pain states. General objective: Adopting a translational approach, we explored the association between the functionality (central & peripheral) of monoaminergic neurotransmission and the efficacy of descending inhibitory mechanisms during the development and progression of chronic pain. Clinical results: Our results replicate several observations emanating from the literature demonstrating a diminution in the efficacy of descending pain inhibitory mechanisms (using a conditioned pain modulation paradigm; CPM) in subjects with chronic musculoskeletal pain (CP subjects). In these CP subjects, we also highlight a reduction in basal plasma concentrations of noradrenaline and metanephrine, when compared with pain-free subjects (PF subjects). For all tested subjects (PF and CP subjects), a positive association is observed between CPM efficacy and basal plasma concentrations of noradrenaline and metanephrine. Therefore, basal plasma catecholamines concentrations could be used as molecular indicators of the latent CPM efficacy. Conversely, no difference in monoaminergic activity and no association with CPM efficacy are observed when looking at the molecular content of cerebrospinal fluid. Preclinical results: Here, we expose a new double-hit model of pain in rodents (i.e., initial induction of a persistent pain [the 1st hit] and subsequent activation of descending pain modulatory mechanisms with tonic pain [the 2nd hit]). This experimental paradigm allows us to evaluate the efficacy of decending pain modulation in rodents in the context of chronic pain. Interestingly, we detect a reduction in the behavioral response to tonic pain (in the formalin test), 28 days after the induction of neuropathic pain (chronic constriction injury model; CCI), when compared to sham rats. Even though this reduction in nociceptive behaviors is still present 168 days after neuropathy, the effect seems to wane down over time. Concomitantly, in absence of tonic nociceptive stimulation, an elevation in central concentrations (i.e., cerebrospinal fluid) in serotonin and noradrenaline is observed 12 days after the induction of neuropathic pain, before returning to sham levels on day 28. Moreover, the behavioral response described on day 28 is only observed in a neuropathic pain model (CCI), and absent when inflammatory pain is used as the initial pain. Conclusions: In the context of chronic pain, our results in humans confirm the advent of modifications in the efficacy of descending pain inhibitory mechanisms, while supporting the emerging concept suggesting that individual differences in these mechanisms may be associated with individual differences in peripheral processes (such as the release of catecholamines in plasma), that could ultimately be involved in cardiovascular control. Moreover, our results in rodents suggest that dynamic changes (specific to pain types) in the efficacy of descending pain modulation, as well as in the central functionality of monoaminergic neurotransmission, are present during the progression of chronic pain. Overall, this thesis provides novel information concerning temporal neurophysiological changes in descending pain modulatory mechanisms that may be involved in the development and progression of chronic pain states.

Doenças, como a enterite necrótica aviária (NE), têm se tornado reemergentes em função não apenas do sistema de criação intensivo de frangos de corte atualmente em uso, como também da restrição imposta ao uso dos aditivos antimicrobianos por diversos países, dentre os quais, aqueles da União Européia. A NE é uma doença que acomete aves de produção e seu agente etiológico primário é o Clostridium perfringens tipo A. Pouco se conhece a respeito dos mecanismos pelos quais o estresse modula o desenvolvimento da NE. O presente trabalho foi realizado para avaliar os efeitos do estresse por calor sobre o desenvolvimento da NE em frangos de corte. Empregou-se, para tal, modelos experimentais de NE em que se usou infecção isolada por C. perfringens e/ou em co-infecção com Eimeria spp. O estresse por calor foi aplicado de forma contínua ou intermitente em longo prazo. Foram propostos sete experimentos; em cinco deles os animais foram criados em câmaras isoladoras e, nos dois restantes, em galpões. Foram feitas avaliações da imunidade sistêmica, de órgãos linfoides secundários e do intestino delgado para determinar os efeitos imunomodulatórios da infecção e/ou do estresse por calor. Para caracterização dos efeitos neuroimunes, fizemos uma análise integrada dos achados imunes, de atividade do Sistema Nervoso Central e/ou de ativação do eixo hipotálamo-hipófise-adrenal (HPA). Foram utilizadas medidas quantitativas e semiquantitativas para avaliar os diferentes graus de lesão tecidual decorrentes do processo infeccioso e/ou parasitário com ou sem estresse por calor. Para analisar os efeitos do estresse no processo infeccioso/parasitário empregamos, também, cultivos microbiológicos e técnicas usadas para determinação da proliferação do C. perfringens e da Eimeria spp. Os resultados mostraram que o estresse por calor: reduziu a inflamação intestinal e o dano tecidual em modelo de NE empregando infecção isolada por C. perfringens preparada em caldo tioglicolato; reduziu a formação de centros germinais esplênicos e intestinais com consequente modulação da produção de imunoglobulinas séricas e secretórias; ativou núcleos do SNC relacionados á atividade do eixo HPA; ativou o eixo cérebro-intestinal; diminuiu a infecção intestinal por Eimeria spp., com consequente redução do desenvolvimento da NE e da lesão tecidual dela resultante; modulou a atividade de sistemas de neurotransmissão central relacionados com o comportamento das aves e ativação do eixo HPA; alterou o perfil neuroquímico cerebral quando em associação com a NE; facilitou o desenvolvimento da infecção por C. perfringens em animais não desafiados por fatores predisponentes da NE; reduziu a lesão tecidual no modelo de co-infecção por C. perfringens e Eimeria spp.; modulou o balanço de citocinas para um padrão Th2 no intestino dos animais infectados ou não; alterou as subpopulações de linfócitos esplênicos e circulantes, bem como a função proliferativa destas células e a resposta das mesmas à expressão de citocinas. Desta forma, concluímos que o estresse por calor e/ou inflamação intestinal de origem infecciosa ou química ativam o eixo HPA por mecanismo que envolve o eixo cérebro-intestinal, reduzindo os sinais clínicos da NE por interferir na patogênese do C. perfringens e da Eimeria spp / Diseases such as necrotic enteritis (NE) are coming back not only as a consequence of the intensive farming procedures now being used but also as a consequence of the restrictions imposed by the European Union countries to the use of antimicrobials as feed additives. NE is a disease that affects poultry production; its primary etiologic agent is Clostridium perfringens type A. Little is known about the mechanisms by which stress modulates the development of NE. Thus, to evaluate the effects of heat stress on NE development, sevenstudies were done using experimental models of NE that used C. perfringens infection per se or in combination with Eimeria spp. Heat stress was used throughout the experiments, being applied continuously or intermittently but always for long-term. Five experiments were performed using animals reared in isolator chambers and two others employing animals reared in sheds. Evaluations of systemic immunity, secondary lymphoid organs and small intestine portions were used to determine the immunomodulatory effects of the infections and/or of the heat stress. Neuroimmune effects were assessed using an integrative approach of the observed immune, Central Nervous System (CNS) and/or hypothalamic-pituitary-adrenal (HPA) axis changes. Quantitative and semi-quantitative techniques were utilized to measure and compare the different degrees of tissue damage resulting from the infectious processes in the presence and absence of heat stress. Microbiological techniques were also used to determine C. perfringens and Eimeria spp. proliferations. Results showed that heat stress: reduced intestinal inflammation and tissue damage in the NE model that used C. perfringens together with thioglycolate broth culture medium intake; reduced the formation of splenic and intestinal germinal centers with subsequent production of serum and secretory immunoglobulins; activated some brain areas related to animals behavior and HPA axis activity; modified the brain-gut axis relationship during NE development; reduced Eimeria spp. infection leading to a subsequent reduction in the NE development and in the scores of tissue injury; together with NE, modified neuronal brain-amine systems activity and, as a consequence, changed animals behavior, HPA axis activity and brain amine systems fuction within some brain areas; predisposed the birds to C. perfringens infection in the presence or absence of NE inducing factors; reduced the tissue damages observed in the course of C. perfringens and Eimeria spp.co-infection; modulated cytokines to a Th2 pattern in animals infected or not; altered the splenic and peripheral blood lymphocytes subpopulations and, changed the proliferative function of immune cells and cytokine expression.Thus, we conclude that the heat stress and/or intestinal inflammation of infectious or chemical origin activate the HPA axis by a mechanism involving the brain-gut axis, reducing the clinical signs of NE by interfering in the pathogenesis of C. perfringens and Eimeria spp

Uliginosina B é um derivado acilfloroglucinol natural, isolado de espécies de Hypericum nativas da América do Sul. Estudos prévios demonstraram que a uliginosina B apresenta efeitos do tipo antidepressivo e antinociceptivo em baixas doses (até 15 mg/kg, i.p. ou v.o.) e, em doses elevadas (90 mg/kg, i.p.), prejudica a coordenação motora. A atividade antidepressiva depende da ativação da neurotransmissão monoaminérgica e envolve a regulação da homeostase através do balanço de Na+. A atividade antinociceptiva é mediada por receptores opioides e dopaminérgicos da família D2. O efeito atáxico depende da ativação de receptores opioides e dopaminérgicos. Os efeitos parecem ser decorrentes da sua capacidade de inibir a recaptação de monoaminas (especialmente dopamina) com consequente ativação de receptores opioides e monoaminérgicos. O objetivo deste estudo foi aprofundar o conhecimento sobre o mecanismo de ação antinociceptiva de uliginosina B, investigando o envolvimento da neurotransmissão monoaminérgica, glutamatérgica e purinérgica. O tratamento com uliginosina B aumentou a disponibilidade intersticial de dopamina e seu metabólito, ácido homovanílico (HVA), no estriado de ratos; dados que reforçam o papel da neurotransmissão dopaminérgica nos efeitos da uliginosina B. O papel das outras monoaminas e da neurotransmissão glutamatérgica foi investigado nos efeitos antinociceptivo e atáxico induzidos por uliginosina B. A ataxia (90 mg/kg, i.p.) foi completamente prevenida pelo tratamento prévio com pCPA (inibidor da síntese de serotonina) e MK-801 (antagonista do receptor glutamatérgico NMDA), mas não foi afetada pelo prétratamento com prazosina ou ioimbina (antagonistas de receptores adrenérgicos α1 e α2, respectivamente). A atividade antinociceptiva (15 e 90 mg/kg, i.p.) foi reduzida significativamente pelo pré-tratamento com pCPA e MK-801 e aumentada pelo prétratamento com prazosina e ioimbina, apenas na dose mais elevada (90 mg/kg, i.p.). A importância da neurotransmissão monoaminérgica para o efeito antinociceptivo da uliginosina B foi confirmada através da análise isobolar. A associação de uliginosina B com amitriptilina (inibidor da recaptação de monoaminas) ou clonidina (agonista adrenérgico α2) apresentou interação aditiva – dados sugestivos de substâncias com mecanismos de ação mediados pelas mesmas vias – enquanto a associação com morfina (agonista opioide) apresentou interação sinérgica – dados indicativos de um possível uso clínico, como adjuvante opioide na farmacoterapia da dor. O efeito antinociceptivo de uliginosina B (15 mg/kg, i.p.) também foi prevenido pelo tratamento prévio com DPCPX e ZM-241385 (antagonistas de receptores adenosinérgicos A1 e A2A, respectivamente). Este efeito esta relacionado, pelo menos em parte, com a capacidade da uliginosina B aumentar a hidrólise de AMP na medula espinhal e de ATP no córtex cerebral. A uliginosina B também inibiu in vitro a atividade da enzima Na+,K+-ATPase (isoformas α1 e α3). O conjunto de dados apresentados nesta tese evidencia a uliginosina B como um padrão estrutural multirreceptor promissor no desenvolvimento de fármacos com ação analgésica. Em suma, os efeitos antinociceptivo e atáxico induzidos pelo tratamento com uliginosina B são mediados pela ativação da neurotransmissão monoaminérgica, glutamatérgica, purinérgica e opióide, requisitadas com diferente grau de importância; e ainda envolvem o balaço iônico da Na+,K+-ATPase. / Uliginosin B is a natural acylphloroglucinol derivative obtained from Hypericum species native to South America. Previous studies have shown that uliginosin B presents antidepressant-like and antinociceptive effects at low doses (up to 15 mg/kg, i.p. or p.o.), and at high doses (90 mg/kg, i.p.) it impairs the motor coordination. The antidepressant-like activity seems to depend on the activation of monoaminergic neurotransmission and ionic balance of Na+. The antinociceptive effect is mediated by opioid and D2 dopamine receptors. The ataxic effect involves opioid and dopaminergic receptors activation. The uliginosin B effects appear to be a consequence of their ability to inhibit reuptake of monoamines (especially dopamine) with subsequent activation of opioid and monoaminergic receptors. The aim of this study was to deepen our knowledge about the mechanism of antinociceptive action of uliginosin B, investigating the involvement of monoaminergic, glutamatergic and purinergic neurotransmissions. Treatment with uliginosin B increased the interstitial availability of dopamine and its metabolite, homovanillic acid (HVA), in the striatum of rats; these data underscore the role of dopaminergic neurotransmission in the effects of uliginosin B. The role of other monoamines as well as the glutamatergic neurotransmission, were investigated in the antinociceptive and ataxic effects induced by uliginosin B. The ataxic effect (90 mg/kg, i.p.) was completely prevented by pre-treatment with pCPA (a serotonin synthesis inhibitor) and MK-801 (a NMDA glutamatergic receptor antagonist), but was not affected by pretreatment with prazosin or yohimbine (α1 and α2 adrenoceptor antagonists, respectively). The antinociceptive activity (15 and 90 mg/kg, i.p.) was significantly reduced by pretreatment with pCPA and MK-801 and increased by pretreatment with yohimbine and prazosin only at the highest dose (90 mg/kg, i.p.). The importance of monoaminergic neurotransmission for the uliginosin B antinociceptive effect was confirmed by isobolar analysis. The association between uliginosin B with amitriptyline (monoamine reuptake inhibitor) or clonidine (α2 adrenergic agonist) showed additive interaction - findings suggestive of substances with mechanisms of action mediated by the same pathways - while the association with morphine (opioid agonist) showed synergistic interaction - indicative of a possible clinical use as adjuvant to opioid pharmacotherapy of pain relief. The antinociceptive effect of uliginosin B (15 mg/kg, i.p.) was also prevented by pretreatment with DPCPX and ZM-241385 (A1 and A2A adenosinergic receptor antagonists, respectively). This effect is related, at least in part, to its ability of increases the AMP and ATP hydrolysis in the spinal cord and cerebral cortex synaptosomes, respectively. Moreover, uliginosin B inhibited the Na+,K+-ATPase activity (α1 and α3 isoforms) in vitro. The data set presented in this thesis pointed uliginosin B as a promising multirreceptor molecular pattern in the analgesic drug development. In summary, the antinociceptive and ataxic effects induced by uliginosin B were mediated by the activation of monoaminergic, glutamatergic, purinérgico and opioid neurotransmission and involves the ionic balance, required with different degree of importance.

Doenças, como a enterite necrótica aviária (NE), têm se tornado reemergentes em função não apenas do sistema de criação intensivo de frangos de corte atualmente em uso, como também da restrição imposta ao uso dos aditivos antimicrobianos por diversos países, dentre os quais, aqueles da União Européia. A NE é uma doença que acomete aves de produção e seu agente etiológico primário é o Clostridium perfringens tipo A. Pouco se conhece a respeito dos mecanismos pelos quais o estresse modula o desenvolvimento da NE. O presente trabalho foi realizado para avaliar os efeitos do estresse por calor sobre o desenvolvimento da NE em frangos de corte. Empregou-se, para tal, modelos experimentais de NE em que se usou infecção isolada por C. perfringens e/ou em co-infecção com Eimeria spp. O estresse por calor foi aplicado de forma contínua ou intermitente em longo prazo. Foram propostos sete experimentos; em cinco deles os animais foram criados em câmaras isoladoras e, nos dois restantes, em galpões. Foram feitas avaliações da imunidade sistêmica, de órgãos linfoides secundários e do intestino delgado para determinar os efeitos imunomodulatórios da infecção e/ou do estresse por calor. Para caracterização dos efeitos neuroimunes, fizemos uma análise integrada dos achados imunes, de atividade do Sistema Nervoso Central e/ou de ativação do eixo hipotálamo-hipófise-adrenal (HPA). Foram utilizadas medidas quantitativas e semiquantitativas para avaliar os diferentes graus de lesão tecidual decorrentes do processo infeccioso e/ou parasitário com ou sem estresse por calor. Para analisar os efeitos do estresse no processo infeccioso/parasitário empregamos, também, cultivos microbiológicos e técnicas usadas para determinação da proliferação do C. perfringens e da Eimeria spp. Os resultados mostraram que o estresse por calor: reduziu a inflamação intestinal e o dano tecidual em modelo de NE empregando infecção isolada por C. perfringens preparada em caldo tioglicolato; reduziu a formação de centros germinais esplênicos e intestinais com consequente modulação da produção de imunoglobulinas séricas e secretórias; ativou núcleos do SNC relacionados á atividade do eixo HPA; ativou o eixo cérebro-intestinal; diminuiu a infecção intestinal por Eimeria spp., com consequente redução do desenvolvimento da NE e da lesão tecidual dela resultante; modulou a atividade de sistemas de neurotransmissão central relacionados com o comportamento das aves e ativação do eixo HPA; alterou o perfil neuroquímico cerebral quando em associação com a NE; facilitou o desenvolvimento da infecção por C. perfringens em animais não desafiados por fatores predisponentes da NE; reduziu a lesão tecidual no modelo de co-infecção por C. perfringens e Eimeria spp.; modulou o balanço de citocinas para um padrão Th2 no intestino dos animais infectados ou não; alterou as subpopulações de linfócitos esplênicos e circulantes, bem como a função proliferativa destas células e a resposta das mesmas à expressão de citocinas. Desta forma, concluímos que o estresse por calor e/ou inflamação intestinal de origem infecciosa ou química ativam o eixo HPA por mecanismo que envolve o eixo cérebro-intestinal, reduzindo os sinais clínicos da NE por interferir na patogênese do C. perfringens e da Eimeria spp / Diseases such as necrotic enteritis (NE) are coming back not only as a consequence of the intensive farming procedures now being used but also as a consequence of the restrictions imposed by the European Union countries to the use of antimicrobials as feed additives. NE is a disease that affects poultry production; its primary etiologic agent is Clostridium perfringens type A. Little is known about the mechanisms by which stress modulates the development of NE. Thus, to evaluate the effects of heat stress on NE development, sevenstudies were done using experimental models of NE that used C. perfringens infection per se or in combination with Eimeria spp. Heat stress was used throughout the experiments, being applied continuously or intermittently but always for long-term. Five experiments were performed using animals reared in isolator chambers and two others employing animals reared in sheds. Evaluations of systemic immunity, secondary lymphoid organs and small intestine portions were used to determine the immunomodulatory effects of the infections and/or of the heat stress. Neuroimmune effects were assessed using an integrative approach of the observed immune, Central Nervous System (CNS) and/or hypothalamic-pituitary-adrenal (HPA) axis changes. Quantitative and semi-quantitative techniques were utilized to measure and compare the different degrees of tissue damage resulting from the infectious processes in the presence and absence of heat stress. Microbiological techniques were also used to determine C. perfringens and Eimeria spp. proliferations. Results showed that heat stress: reduced intestinal inflammation and tissue damage in the NE model that used C. perfringens together with thioglycolate broth culture medium intake; reduced the formation of splenic and intestinal germinal centers with subsequent production of serum and secretory immunoglobulins; activated some brain areas related to animals behavior and HPA axis activity; modified the brain-gut axis relationship during NE development; reduced Eimeria spp. infection leading to a subsequent reduction in the NE development and in the scores of tissue injury; together with NE, modified neuronal brain-amine systems activity and, as a consequence, changed animals behavior, HPA axis activity and brain amine systems fuction within some brain areas; predisposed the birds to C. perfringens infection in the presence or absence of NE inducing factors; reduced the tissue damages observed in the course of C. perfringens and Eimeria spp.co-infection; modulated cytokines to a Th2 pattern in animals infected or not; altered the splenic and peripheral blood lymphocytes subpopulations and, changed the proliferative function of immune cells and cytokine expression.Thus, we conclude that the heat stress and/or intestinal inflammation of infectious or chemical origin activate the HPA axis by a mechanism involving the brain-gut axis, reducing the clinical signs of NE by interfering in the pathogenesis of C. perfringens and Eimeria spp

Le modèle de sensibilisation comportementale permet d'étudier les changements neuronaux induits par les drogues. Chez les rongeurs, l'activité locomotrice augmente au fur et à mesure des injections et se maintient à long terme. En parallèle à cette sensibilisation, on observe une sensibilisation neurochimique des transmissions noradrénergique (NA) et sérotoninergique (5-HT) jusqu'à un mois après la dernière injection. Cette sensibilisation neurochimique, qui se traduit par des libérations de NA et de 5-HT potentialisées mesurées au niveau du cortex préfrontal, est commune à toutes les drogues et fortement corrélée à la sensibilisation comportementale. Le but de ce travail était d'identifier les mécanismes qui maintiennent à long terme cette hyper-réactivité. Nous avons tout d'abord montré que la réponse locomotrice potentialisée à l'amphétamine se maintient durant le premier mois de sevrage, et décroit de 60% entre 2 et 4 mois. Toutefois les souris restent plus vulnérables à la drogue et ce, même après de longs sevrages. Nous avons également démontré que l'hyper-réactivité des systèmes se maintient à long terme notamment grâce à une désensibilisation fonctionnelle persistante des récepteurs ?2A- adrénergiques et 5-HT1A, responsables du rétrocontrôle inhibiteur des transmissions NA et 5-HT. On observe une diminution de l'expression des protéines G?i couplées à ces récepteurs, dans le locus coeruleus et dans le raphé dorsal, respectivement. La même altération des rétrocontrôles ayant été mesurée chez les animaux sensibilisés au MDMA, les résultats suggèrent que les récepteurs ?2A-adrénergiques et 5-HT1A pourraient être des cibles indirectes des psychostimulants.

La protéine STOP (MAP6) associée aux microtubules joue un rôle clé dans l'architecture neuronale et la plasticité synaptique, dont les dysfonctionnements sont considérés comme étant impliqués dans la physiopathologie des maladies psychiatriques. En accord avec cette hypothèse, la délétion de la protéine STOP chez la souris, conduit à des altérations neuroanatomiques, biochimiques et comportementales, en partie atténuées par des traitements antipsychotiques. Dans cette étude, nous avons tout d'abord examiné les possibles altérations des systèmes monoaminergiques chez les souris STOP KO. Chez les souris mutantes, les marqueurs sérotoninergiques et noradrénergiques sont accumulés dans le mésencéphale et, au contraire fortement diminués dans toutes les régions de projections du cerveau antérieur. De plus, ces déséquilibres monoaminergiques sont associés à une augmentation du statut dépressif, une diminution du statut anxieux et des déficits dans des tâches d'apprentissage et de mémorisation. Les effets d'un traitement chronique par la fluoxétine ou par l'épothilone D, un composé analogue du taxol stabilisant les microtubules, sur l'humeur et les performances cognitives des souris STOP KO ont aussi été évalués. Le traitement chronique par la fluoxétine induit des effets paradoxaux sur le statut dépressif et le statut anxieux des souris STOP KO suivant les tests effectués, probablement à cause d'une hypersensibilité au stress. En revanche, les traitements chroniques à la fluoxétine et à l'épothilone D ont amélioré la mémoire à court terme des souris STOP KO. Dans l'ensemble, ces résultats indiquent que la délétion de la protéine STOP chez la souris induit de fortes altérations de l'humeur et des performances cognitives et que la protéine STOP pourrait avoir un rôle crucial dans le développement des systèmes monoaminergiques.

Uliginosina B é um derivado acilfloroglucinol natural, isolado de espécies de Hypericum nativas da América do Sul. Estudos prévios demonstraram que a uliginosina B apresenta efeitos do tipo antidepressivo e antinociceptivo em baixas doses (até 15 mg/kg, i.p. ou v.o.) e, em doses elevadas (90 mg/kg, i.p.), prejudica a coordenação motora. A atividade antidepressiva depende da ativação da neurotransmissão monoaminérgica e envolve a regulação da homeostase através do balanço de Na+. A atividade antinociceptiva é mediada por receptores opioides e dopaminérgicos da família D2. O efeito atáxico depende da ativação de receptores opioides e dopaminérgicos. Os efeitos parecem ser decorrentes da sua capacidade de inibir a recaptação de monoaminas (especialmente dopamina) com consequente ativação de receptores opioides e monoaminérgicos. O objetivo deste estudo foi aprofundar o conhecimento sobre o mecanismo de ação antinociceptiva de uliginosina B, investigando o envolvimento da neurotransmissão monoaminérgica, glutamatérgica e purinérgica. O tratamento com uliginosina B aumentou a disponibilidade intersticial de dopamina e seu metabólito, ácido homovanílico (HVA), no estriado de ratos; dados que reforçam o papel da neurotransmissão dopaminérgica nos efeitos da uliginosina B. O papel das outras monoaminas e da neurotransmissão glutamatérgica foi investigado nos efeitos antinociceptivo e atáxico induzidos por uliginosina B. A ataxia (90 mg/kg, i.p.) foi completamente prevenida pelo tratamento prévio com pCPA (inibidor da síntese de serotonina) e MK-801 (antagonista do receptor glutamatérgico NMDA), mas não foi afetada pelo prétratamento com prazosina ou ioimbina (antagonistas de receptores adrenérgicos α1 e α2, respectivamente). A atividade antinociceptiva (15 e 90 mg/kg, i.p.) foi reduzida significativamente pelo pré-tratamento com pCPA e MK-801 e aumentada pelo prétratamento com prazosina e ioimbina, apenas na dose mais elevada (90 mg/kg, i.p.). A importância da neurotransmissão monoaminérgica para o efeito antinociceptivo da uliginosina B foi confirmada através da análise isobolar. A associação de uliginosina B com amitriptilina (inibidor da recaptação de monoaminas) ou clonidina (agonista adrenérgico α2) apresentou interação aditiva – dados sugestivos de substâncias com mecanismos de ação mediados pelas mesmas vias – enquanto a associação com morfina (agonista opioide) apresentou interação sinérgica – dados indicativos de um possível uso clínico, como adjuvante opioide na farmacoterapia da dor. O efeito antinociceptivo de uliginosina B (15 mg/kg, i.p.) também foi prevenido pelo tratamento prévio com DPCPX e ZM-241385 (antagonistas de receptores adenosinérgicos A1 e A2A, respectivamente). Este efeito esta relacionado, pelo menos em parte, com a capacidade da uliginosina B aumentar a hidrólise de AMP na medula espinhal e de ATP no córtex cerebral. A uliginosina B também inibiu in vitro a atividade da enzima Na+,K+-ATPase (isoformas α1 e α3). O conjunto de dados apresentados nesta tese evidencia a uliginosina B como um padrão estrutural multirreceptor promissor no desenvolvimento de fármacos com ação analgésica. Em suma, os efeitos antinociceptivo e atáxico induzidos pelo tratamento com uliginosina B são mediados pela ativação da neurotransmissão monoaminérgica, glutamatérgica, purinérgica e opióide, requisitadas com diferente grau de importância; e ainda envolvem o balaço iônico da Na+,K+-ATPase. / Uliginosin B is a natural acylphloroglucinol derivative obtained from Hypericum species native to South America. Previous studies have shown that uliginosin B presents antidepressant-like and antinociceptive effects at low doses (up to 15 mg/kg, i.p. or p.o.), and at high doses (90 mg/kg, i.p.) it impairs the motor coordination. The antidepressant-like activity seems to depend on the activation of monoaminergic neurotransmission and ionic balance of Na+. The antinociceptive effect is mediated by opioid and D2 dopamine receptors. The ataxic effect involves opioid and dopaminergic receptors activation. The uliginosin B effects appear to be a consequence of their ability to inhibit reuptake of monoamines (especially dopamine) with subsequent activation of opioid and monoaminergic receptors. The aim of this study was to deepen our knowledge about the mechanism of antinociceptive action of uliginosin B, investigating the involvement of monoaminergic, glutamatergic and purinergic neurotransmissions. Treatment with uliginosin B increased the interstitial availability of dopamine and its metabolite, homovanillic acid (HVA), in the striatum of rats; these data underscore the role of dopaminergic neurotransmission in the effects of uliginosin B. The role of other monoamines as well as the glutamatergic neurotransmission, were investigated in the antinociceptive and ataxic effects induced by uliginosin B. The ataxic effect (90 mg/kg, i.p.) was completely prevented by pre-treatment with pCPA (a serotonin synthesis inhibitor) and MK-801 (a NMDA glutamatergic receptor antagonist), but was not affected by pretreatment with prazosin or yohimbine (α1 and α2 adrenoceptor antagonists, respectively). The antinociceptive activity (15 and 90 mg/kg, i.p.) was significantly reduced by pretreatment with pCPA and MK-801 and increased by pretreatment with yohimbine and prazosin only at the highest dose (90 mg/kg, i.p.). The importance of monoaminergic neurotransmission for the uliginosin B antinociceptive effect was confirmed by isobolar analysis. The association between uliginosin B with amitriptyline (monoamine reuptake inhibitor) or clonidine (α2 adrenergic agonist) showed additive interaction - findings suggestive of substances with mechanisms of action mediated by the same pathways - while the association with morphine (opioid agonist) showed synergistic interaction - indicative of a possible clinical use as adjuvant to opioid pharmacotherapy of pain relief. The antinociceptive effect of uliginosin B (15 mg/kg, i.p.) was also prevented by pretreatment with DPCPX and ZM-241385 (A1 and A2A adenosinergic receptor antagonists, respectively). This effect is related, at least in part, to its ability of increases the AMP and ATP hydrolysis in the spinal cord and cerebral cortex synaptosomes, respectively. Moreover, uliginosin B inhibited the Na+,K+-ATPase activity (α1 and α3 isoforms) in vitro. The data set presented in this thesis pointed uliginosin B as a promising multirreceptor molecular pattern in the analgesic drug development. In summary, the antinociceptive and ataxic effects induced by uliginosin B were mediated by the activation of monoaminergic, glutamatergic, purinérgico and opioid neurotransmission and involves the ionic balance, required with different degree of importance.

Uliginosina B é um derivado acilfloroglucinol natural, isolado de espécies de Hypericum nativas da América do Sul. Estudos prévios demonstraram que a uliginosina B apresenta efeitos do tipo antidepressivo e antinociceptivo em baixas doses (até 15 mg/kg, i.p. ou v.o.) e, em doses elevadas (90 mg/kg, i.p.), prejudica a coordenação motora. A atividade antidepressiva depende da ativação da neurotransmissão monoaminérgica e envolve a regulação da homeostase através do balanço de Na+. A atividade antinociceptiva é mediada por receptores opioides e dopaminérgicos da família D2. O efeito atáxico depende da ativação de receptores opioides e dopaminérgicos. Os efeitos parecem ser decorrentes da sua capacidade de inibir a recaptação de monoaminas (especialmente dopamina) com consequente ativação de receptores opioides e monoaminérgicos. O objetivo deste estudo foi aprofundar o conhecimento sobre o mecanismo de ação antinociceptiva de uliginosina B, investigando o envolvimento da neurotransmissão monoaminérgica, glutamatérgica e purinérgica. O tratamento com uliginosina B aumentou a disponibilidade intersticial de dopamina e seu metabólito, ácido homovanílico (HVA), no estriado de ratos; dados que reforçam o papel da neurotransmissão dopaminérgica nos efeitos da uliginosina B. O papel das outras monoaminas e da neurotransmissão glutamatérgica foi investigado nos efeitos antinociceptivo e atáxico induzidos por uliginosina B. A ataxia (90 mg/kg, i.p.) foi completamente prevenida pelo tratamento prévio com pCPA (inibidor da síntese de serotonina) e MK-801 (antagonista do receptor glutamatérgico NMDA), mas não foi afetada pelo prétratamento com prazosina ou ioimbina (antagonistas de receptores adrenérgicos α1 e α2, respectivamente). A atividade antinociceptiva (15 e 90 mg/kg, i.p.) foi reduzida significativamente pelo pré-tratamento com pCPA e MK-801 e aumentada pelo prétratamento com prazosina e ioimbina, apenas na dose mais elevada (90 mg/kg, i.p.). A importância da neurotransmissão monoaminérgica para o efeito antinociceptivo da uliginosina B foi confirmada através da análise isobolar. A associação de uliginosina B com amitriptilina (inibidor da recaptação de monoaminas) ou clonidina (agonista adrenérgico α2) apresentou interação aditiva – dados sugestivos de substâncias com mecanismos de ação mediados pelas mesmas vias – enquanto a associação com morfina (agonista opioide) apresentou interação sinérgica – dados indicativos de um possível uso clínico, como adjuvante opioide na farmacoterapia da dor. O efeito antinociceptivo de uliginosina B (15 mg/kg, i.p.) também foi prevenido pelo tratamento prévio com DPCPX e ZM-241385 (antagonistas de receptores adenosinérgicos A1 e A2A, respectivamente). Este efeito esta relacionado, pelo menos em parte, com a capacidade da uliginosina B aumentar a hidrólise de AMP na medula espinhal e de ATP no córtex cerebral. A uliginosina B também inibiu in vitro a atividade da enzima Na+,K+-ATPase (isoformas α1 e α3). O conjunto de dados apresentados nesta tese evidencia a uliginosina B como um padrão estrutural multirreceptor promissor no desenvolvimento de fármacos com ação analgésica. Em suma, os efeitos antinociceptivo e atáxico induzidos pelo tratamento com uliginosina B são mediados pela ativação da neurotransmissão monoaminérgica, glutamatérgica, purinérgica e opióide, requisitadas com diferente grau de importância; e ainda envolvem o balaço iônico da Na+,K+-ATPase. / Uliginosin B is a natural acylphloroglucinol derivative obtained from Hypericum species native to South America. Previous studies have shown that uliginosin B presents antidepressant-like and antinociceptive effects at low doses (up to 15 mg/kg, i.p. or p.o.), and at high doses (90 mg/kg, i.p.) it impairs the motor coordination. The antidepressant-like activity seems to depend on the activation of monoaminergic neurotransmission and ionic balance of Na+. The antinociceptive effect is mediated by opioid and D2 dopamine receptors. The ataxic effect involves opioid and dopaminergic receptors activation. The uliginosin B effects appear to be a consequence of their ability to inhibit reuptake of monoamines (especially dopamine) with subsequent activation of opioid and monoaminergic receptors. The aim of this study was to deepen our knowledge about the mechanism of antinociceptive action of uliginosin B, investigating the involvement of monoaminergic, glutamatergic and purinergic neurotransmissions. Treatment with uliginosin B increased the interstitial availability of dopamine and its metabolite, homovanillic acid (HVA), in the striatum of rats; these data underscore the role of dopaminergic neurotransmission in the effects of uliginosin B. The role of other monoamines as well as the glutamatergic neurotransmission, were investigated in the antinociceptive and ataxic effects induced by uliginosin B. The ataxic effect (90 mg/kg, i.p.) was completely prevented by pre-treatment with pCPA (a serotonin synthesis inhibitor) and MK-801 (a NMDA glutamatergic receptor antagonist), but was not affected by pretreatment with prazosin or yohimbine (α1 and α2 adrenoceptor antagonists, respectively). The antinociceptive activity (15 and 90 mg/kg, i.p.) was significantly reduced by pretreatment with pCPA and MK-801 and increased by pretreatment with yohimbine and prazosin only at the highest dose (90 mg/kg, i.p.). The importance of monoaminergic neurotransmission for the uliginosin B antinociceptive effect was confirmed by isobolar analysis. The association between uliginosin B with amitriptyline (monoamine reuptake inhibitor) or clonidine (α2 adrenergic agonist) showed additive interaction - findings suggestive of substances with mechanisms of action mediated by the same pathways - while the association with morphine (opioid agonist) showed synergistic interaction - indicative of a possible clinical use as adjuvant to opioid pharmacotherapy of pain relief. The antinociceptive effect of uliginosin B (15 mg/kg, i.p.) was also prevented by pretreatment with DPCPX and ZM-241385 (A1 and A2A adenosinergic receptor antagonists, respectively). This effect is related, at least in part, to its ability of increases the AMP and ATP hydrolysis in the spinal cord and cerebral cortex synaptosomes, respectively. Moreover, uliginosin B inhibited the Na+,K+-ATPase activity (α1 and α3 isoforms) in vitro. The data set presented in this thesis pointed uliginosin B as a promising multirreceptor molecular pattern in the analgesic drug development. In summary, the antinociceptive and ataxic effects induced by uliginosin B were mediated by the activation of monoaminergic, glutamatergic, purinérgico and opioid neurotransmission and involves the ionic balance, required with different degree of importance.

In humans and other organisms, monoaminergic systems are crucial in neuronal function and behavior. The monoamine transporters (MATs), which can be found on the presynaptic plasma membrane of neurons in the central nervous system (CNS), are crucial in the regulation of neurotransmitter concentration in the synaptic cleft. As the duration and concentration of neurotransmitters in the cleft affect further downstream signaling responses, these proteins are important targets for both understanding neuronal physiology and compounds of interest. Multiple theories exist proponing the contribution of MATs to a variety of mental and neurological disorders, including depression. This theory establishes that depression is caused by imbalances in monoamine neurotransmitters. Compounds such as Fluoxetine (FLX) are classified as selective serotonin reuptake inhibitors (SSRIs), these drugs selectively block the reuptake of neurotransmitters at the serotonin transporter (SERT). Since differences in MAT selectivity of inhibitory compounds are influential to selecting efficacious antidepressant treatments, we utilized a unique fluorescent analysis technique to explore three therapeutic compounds of interest (in-vitro) which contain structural similarity to FLX. Our results confirm the selectivity of FLX at SERT, and classify the novel compounds studied into different potential categories of reuptake inhibitors. We hope these compounds will be studied further to elucidate their potentially therapeutic roles and mitigation of undesired side effects seen in other medications.

Posttraumatic stress disorder (PTSD) is an anxiety disorder that may result from an exposure to a severely traumatic life-event. It is characterised by a delayed onset of psychological and physical symptoms including re-experiencing the event, avoidance of reminders associated with the trauma, increased autonomic arousal and distinct memory deficits. This disorder is also characterised by a maladaptive hypothalamic-pituitary-adrenal (HPA)-axis response and altered monoamine concentrations in the hippocampus and pre-frontal cortex. The Time Dependent Sensitization (TDS) model is a putative animal model of PTSD that is based on the concept of repeated trauma, using three acute stressors (TS) of intense severity followed by a mild situational reminder (RS) on day 7 subsequent to the acute stressors. The aims of this study were to determine if the Triple Stressor (TS) induces stress and if the situational reminder (RS) is necessary for the maintenance of the stress response over time and whether these two stress responses are qualitatively and quantitively different. This was done to further validate the TDS model and to characterize the development and progression of the stress-related pathology of PTSD. Methods used were High Performance Liquid Chromatography (HPLC) with electrochemical detection (biochemical correlates) for quantifying the monoamines dopamine (DA), noradrenaline (NA) and serotonin (5-HT) concentrations in the hippocampus and pre-frontal cortex (PFC); radio immuno assay (RIA) for the determination of plasma corticosterone concentrations (neuroendocrine parameter) and the use of the Elevated Plus Maze (EPM) to detect anxiety-like behaviour (behavioural analyses). The study was subdivided into an Acute and Re-Stress study (n = 10). In the Acute Study rats were exposed to TS as the only stressor. Group 1 was sacrificed immediately after TS, Group 2 was sacrificed 3 days post TS and Group 3 on day 7 post TS. In the Re-Stress Study both TS and RS were used as stressors. Group 4 was sacrificed immediately after the situational reminder, Group 5 was sacrificed 3 days post RS and Group 6 on day 7 post RS. A group of unstressed rats were used as Control. The results of this study found corticosterone concentrations elevated immediately after the TS (p<0.05). Exposure to the RS resulted in a profound hypocortisolism (p<0.05). These results indicate a possible disturbance in the regulation of the HPA-axis, which manifests as an enhanced negative feed-back upon re-introduction of the stressful situation. Changes in MA concentrations were evident. Although no definite fixed trend is apparent in this study, it is evident that the TDS model does induce monoamine dysregulation. Hippocampal NA. DA and 5-HT concentrations were noted to be elevated on day 7 post TS (p<0.05). On day 7 post RS only hippocampal 5HT was decreased significantly (p<0.05). Behavioural analyses indicate that stress related anxiety was not sustained after the TS but 7 days after the exposure to the RS rats were most anxious (p<0.05). The results confirm that the TDS model does induce PTSD-like symptoms in rats and that the situational reminder (RS) is necessary for the maintenance of the stress response. This model may be useful in the investigation of future experimental pharmacological interventions in the management of PTSD. / Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2005.