Un lien entre certaines dysfonctions du système sérotoninergique et la survenue de valvulopathies a été suggéré par les lésions valvulaires observées au cours de l’utilisation chronique de certains agonistes des récepteurs 5-HT2 (dérivés de l’ergot de seigle, fenfluramine) et les atteintes tumorales carcinoïdes (qui entrainent une augmentation des taux de 5-HT circulante). Les lésions dégénératives associent une fibrose, une sténose et/ou une régurgitation des valves pouvant conduire à de nombreuses complications cardiovasculaires. À l’heure actuelle, il n’existe aucune thérapeutique pouvant freiner ou faire régresser les lésions. Nos travaux démontrent à partir de modèles animaux et cellulaires, l’implication effective des récepteurs 5-HT2B et 5-HT2A dans l’initiation des lésions. L’analyse histologique des valves à partir de nos modèles animaux a révélé la contribution des cellules endothéliales au cours des stades précoces. Ces cellules sont des progéniteurs endothéliaux (CD34+) recrutés à partir de la moelle au sein de la valve sous la stimulation des récepteurs 5-HT2 et par un mécanisme intracellulaire impliquant la eNOS. Des travaux ultérieurs permettront de mieux caractériser les différents types cellulaires et les biomarqueurs d’initiation du processus afin de déterminer de nouvelles pistes thérapeutiques. / Several studies have reported a strong correlation between the development of cardiac valve injury and some dysfunctions of the serotonergic system. Valve lesions are observed during the chronic use of some 5-HT2 receptors agonists (ergot derivates or fenfluramine derivatives) or are secondary to metastatic carcinoid tumours (with increased circulating 5-HT amount). These lesions show fibrosis, with thickened leaflets, valves stenosis and/or regurgitation followed by several cardiovascular complications. There is no medical treatment to stop or alter the natural course of the lesions. Surgical replacement by prosthesis is the only effective therapy. Our study based on animal and cellular pharmacological models, demonstrates the serotonergic system contribution through 5-HT2B and 5-HT2A receptors in the pathogenesis of valve degeneration. Histological analysis of the lesions reveals the contribution of endothelial cells to the initiation process. These cells are probably endothelial progenitors (CD34+) recruited inside the valve implying a NO-dependent mechanism. Further studies will characterize the specific cells to find biomarkers of valve remodelling initiation and at term, will identify best therapeutic targets around the serotonergic system.

Made available in DSpace on 2016-06-02T19:22:07Z (GMT). No. of bitstreams: 1 4371.pdf: 2307232 bytes, checksum: c294e0a05e2cf2a6bd0b3c04f56a1180 (MD5) Previous issue date: 2011-12-15 / Several lines of evidence support the involvement of serotonergic (5-HT) neurons of the median raphe nucleus (MRN) in anxiety-like behaviour. In this context, it is known that blockade of 5- HT1A somatodendritic autoreceptors in the midbrain raphe nuclei increases the firing rate of these neurons, disinhibiting 5-HT release in postsynaptic target areas such as amygdala, hippocampus and periaqueductal grey matter (PAG). However, while activation of 5-HT1A or 5- HT2 receptors in forebrain targets such as the amygdala or hippocampus enhances anxiety-like behaviours in rodents, stimulation of both receptor subtypes in the midbrain PAG markedly reduces anxiety-like behaviour. In view of these findings, the present study investigated whether the anti-anxiety effects induced by pharmacological disinhibition of 5-HT neurons in the MRN are attenuated by the blockade of 5-HT2 receptors within the PAG. Mice received combined intra-PAG injection with ketanserin (10 nmol/0.1 μl), a 5-HT2 receptor antagonist, followed by intra-MRN injection of WAY-100635 (5.6 nmol/0.l μl), a highly selective 5-HT1A receptor antagonist. They were then individually exposed to the elevated plus-maze (EPM), with the videotaped behavioural sessions subsequently scored for both conventional and ethological measures. The results confirmed that intra-MRN infusion of WAY100635 (5.6 nmol/0.l μl)reduces behavioural indices of anxiety without significantly altering general activity measures, and further showed that this effect was completely blocked by intra-PAG pretreatment with an intrinsically-inactive dose of ketanserin (10 nmol/0.1 μl). Together, these results suggest that 5HT2 receptor populations located within the midbrain PAG play a significant role in the reduction of anxiety observed following disinhibition of 5-HT neurons in the MRN. / Várias evidências apontam o envolvimento de neurônios serotoninérgicos do núcleo mediano da rafe (NMnR) na ansiedade. Sabe-se que o bloqueio dos autorreceptores somatodendríticos dos núcleos da rafe aumenta a taxa de disparo dos neurônios serotoninérgicos, promovendo a liberação de serotonina em sítios pós-sinápticos como amígdala, hipocampo e substância cinzenta periaquedutal (SCP). Contudo, enquanto a ativação de receptores 5-HT1A ou 5-HT2 da amígdala ou hipocampo resulta em aumento da ansiedade em camundongos, a estimulação de ambos os receptores na substância cinzenta periaquedutal resulta em efeitos antiaversivos. Nessa perspectiva, o presente estudo investigou se o efeito ansiolítico induzido pela desinibição farmacológica dos neurônios serotoninérgicos do NMnR é suprimido pelo bloqueio dos receptores 5-HT2 da SCP. Para isso, camundongos receberam injeções combinadas de cetanserina na SCP (10 nmol/0,1μl), antagonista dos receptores 5-HT2B/2C, seguidas por injeções intra-NMnR de WAY100635 (5,6 nmol/0,1μl), antagonista seletivo dos receptores 5-HT1A. Os animais foram, então, individualmente expostos ao labirinto em cruz elevado (LCE) durante cinco minutos. Os testes foram gravados para posterior análise dos índices convencionais e etológicos de ansiedade. Os resultados confirmaram que infusões intra-NMnR de WAY100635 (5,6 nmol/0,1μl) reduzem os parâmetros comportamentais de ansiedade sem alterar índices de atividade locomotora, e que este efeito é completamente bloqueado pelo pré-tratamento com uma dose intrinsecamente inativa de cetanserina (10 nmol/0,1μl) na SCP. Dessa forma, estes resultados sugerem que os receptores 5-HT2 da SCP desempenham um papel significativo na redução da ansiedade observada após a desinibição dos neurônios serotoninérgicos do NMnR.

Made available in DSpace on 2016-06-02T19:22:49Z (GMT). No. of bitstreams: 1 1787.pdf: 881972 bytes, checksum: 8efb2228f3d2702e11bcd0d89eea8eae (MD5) Previous issue date: 2008-03-28 / It is widely acknowledged that the indoleamine neurotransmitter serotonin (5-HT) plays a dual role in the regulation of anxiety, a role that in part depends upon neuroanatomical locus of action. Thus, whereas stimulation of 5-HT1A or 5-HT2 receptors in the limbic forebrain (amygdala, hippocampus) enhances anxiety-like responding in rodents, activation of corresponding receptor populations in the midbrain periaqueductal grey (PAG) more often than not reduces anxiety-like behavior. The present study specifically concerns the anxietymodulating influence of 5-HT2 receptors within the mouse PAG. Experiment 1 assessed the effects of intra-PAG infusions of the 5-HT2B/2C receptor agonist mCPP (0, 0.03, 0.1 or 0.3 nmol/0.1 µl) on the behavior of mice exposed to the elevated plus-maze. Experiment 2 assessed the effects of intra-PAG infusions of the preferential 5-HT2A/2C receptor antagonist ketanserin (0 or 10 nmol/0.1 µl), on the behaviour of mice exposed to the elevated plus-maze. As mCPP acts preferentially at 5-HT2B and 5-HT2C receptors, Experiment 3 investigated its effects in animals pretreated with ketanserin. The test sessions were videotaped and subsequently scored for anxiety-like behaviour (e.g. percentage of open arm entries and percentage of open arm time) as well as general locomotor activity (closed arm entries). The results of Experiment 1 showed that mCPP microinfusions (0.03 and 0.1 nmol) into the PAG of mice decreased behavioural indices of anxiety without significantly altering general activity measures. Results of experiment 2 showed that intra-PAG infusions of ketanserin (10 nmol) did not alter conventional indices of anxiety, nor locomotor activity. In Experiment 3, the anxiolytic-like profile of intra-PAG mCPP (0.03 nmol) was substantially attenuated by intra-PAG pretreatment with an intrinsically-inactive dose of the preferential 5-HT2A/2C receptor antagonist, ketanserin (10 nmol). Together, these data suggest that 5HT2C receptor populations within the midbrain PAG play an inhibitory role in plus-maze anxiety in mice. / Tem sido amplamente reconhecido que a serotonina (5-HT) desempenha um papel dual na regulação da ansiedade, papel este que depende, em parte, do sítio neuroanatômico de ação. Assim, enquanto a estimulação de receptores do subtipo 5-HT1A ou 5-HT2 em estruturas prosencefálicas como amígdala e hipocampo resultam na potencialização de respostas de ansiedade em roedores, a ativação dos mesmos receptores na substância cinzenta periaquedutal (SCP) mesencefálica freqüentemente tende a diminuir comportamentos relacionados à ansiedade. O presente estudo enfoca especificamente a influência dos receptores 5-HT2 da substância cinzenta periaquedutal na modulação da ansiedade em camundongos. O experimento 1 avaliou os efeitos de injeções intra-SCP de mCPP (0, 0,03, 0,01 e 0,3 nmol/0,1 µl), um agonista dos receptores 5-HT2B/2C, sobre o comportamento de camundongos expostos ao Labirinto em Cruz Elevado (LCE). O experimento 2 avaliou os efeitos de injeções intra-SCP do antagonista dos receptores 5-HT2A/2C, cetanserina (0 e 10 nmol/0,1 µl), sobre o comportamento de camundongos submetidos ao LCE. Como o mCPP atua preferencialmente sobre os receptores 5-HT2B e 5-HT2C, o experimento 3 investigou seu efeito em animais pré-tratados com cetanserina. Os testes foram gravados e subseqüentemente registrados para análise dos índices de ansiedade (porcentagem de entradas e porcentagem de tempo gasto nos braços abertos) assim como de atividade locomotora (entradas nos braços fechados). Os resultados do experimento 1 mostram que micromicroinjeções de mCPP (0,03 e 0,1 nmol) na SCP de camundongos diminuíram índices comportamentais de ansiedade sem alterar significativamente medidas de atividade locomotora geral. Dados do experimento 2 mostram que a cetanserina (10 nmol) não alterou os índices convencionais de ansiedade, nem a atividade locomotora dos animais. O experimento 3 demonstra que o perfil ansiolítico do mCPP (0,03 nmol) injetado na SCP foi substancialmente atenuado pelo pré-tratamento intra- SCP de uma dose intrinsecamente inativa do antagonista preferencial dos receptores 5-HT2A/2C, cetanserina (10 nmol). Juntos estes dados sugerem que os receptores 5-HT2C da SCP desempenham um papel inibitório na ansiedade de camundongos submetidos ao LCE.

The mechanisms by which antipsychotics (neuroleptics) produce their therapeutic effects in schizophrenia are largely unknown. Although neuroleptic efficacy is attributed to central dopamine D2 and/or serotonin 5-HT2 receptor antagonism, clinical improvements in schizophrenia are not seen until two or three weeks after daily neuroleptic administration. The mechanisms underlying the neuroleptic response must therefore occur downstream from initial receptor blockade and be a consequence of chronic neurotransmitter receptor blockade. The goal of the present study was to use neuroleptics with varied dopamine vs. serotonergic receptor blocking profiles to elucidate some of these intracellular post receptor mechanisms. Since the final steps of both dopamine and serotonin synthesis require the enzyme aromatic L-amino acid decarboxylase (AADC), the effects of neuroleptics on AADC gene (mRNA) expression were examined in PC12 cells and compared to their effects on the synthetic enzyme tyrosine hydroxylase (TH) and ' c-fos' (an early immediate gene [IEG]) mRNA. The neuroleptics examined did not significantly regulate AADC mRNA in PC12 cells, and only haloperidol upregulated TH and 'c-fos' mRNA. Later studies in rats showed that acute neuroleptic administration increased ' c-fos' mRNA, whereas the immunoreactivity of a related IEG (delta FosB) was increased upon chronic treatment. These studies and a subsequent dose response study demonstrated that upregulation of both 'c-fos' mRNA and delta FosB immunoreactivity was most prominent in dopaminergic projection areas including the striatum and nucleus accumbens. Because it has been suggested that neuroleptic treatment might prevent neurodegeneration in schizophrenia, the effects of neuroleptics on the mRNA expression of neuroprotective target genes of delta FosB were examined both ' in vivo' and 'in vitro'. These genes included brain-derived neurotrophic factor (BDNF), the neuroprotective enzyme superoxide dismutase (SOD), and the low affinity nerve growth factor receptor (p75). While dopamine D2 blockade unfavorably regulated BDNF and p75 mRNA, 5-HT 2 blockade either had no effect on or favorably regulated BDNF, SOD, and p75 mRNA. Thus, although little about the contribution of serotonergic blockade in the neuroleptic response was determined, dopaminergic blockade regulated IEG's and several of their target genes. Future studies will be needed to understand the role of 5-HT2 receptor blockade in the neuroleptic response.

Les inhibiteurs sélectifs de recapture de la sérotonine (5-HT) (ISRS) bloquent directement le transporteur de la 5-HT (SERT) et stimulent indirectement de multiples auto- et hétérorécepteurs5-HT par l’augmentation de la concentration extracellulaire de 5-HT dans la fente synaptique. Cependant, le rôle des différents récepteurs ainsi que leur interaction dans les effets thérapeutiques des ISRS restent mal connus. Nous avons tenté de les identifier à l'aide de tests neurochimiques (microdialyse intracérébrale in vivo) et électrophysiologiques en utilisant une approche pharmacologique (utilisation de escitalopram, de ligands des récepteurs 5-HT1A/2A) et génétique (utilisation de souris knock-out [KO] SERT, 5-HT1A ou 5-HT2A). Les études neurochimiques et électrophysiologiques révèlent que les auto-(1A) et hétéro-(2A) récepteursagissent de concert pour maintenir une influence inhibitrice sur le système sérotoninergique, en particulier, en réponse au escitalopram : l'absence d'un récepteur est compensée par une régulation de l'autre. Enfin, les souris KO SERT constituent un nouveau modèle pour tester le mécanisme du escitalopram dans l’augmentation des concentrations de noradrénaline (NA). / Selective serotonin (5-HT) reuptake inhibitors (SSRIs) directly block the 5-HT transporter(SERT) and indirectly stimulate multiple 5-HT (auto- and hetero-) receptors by enhancing itsextracellular levels in the synaptic cleft, although the role of particular receptors as well asinteraction(s) among different receptors in the therapeutic effects of SSRIs is not fullyunderstood. We tried to highlight it using neurochemical (in vivo intracerebral microdialysis) andelectrophysiological tests with a pharmacological (using escitalopram, 5-HT1A/2A receptorsagonists and antagonists) and genetic (using SERT, 5-HT1A ou 5-HT2A receptor knock-out [KO]mice) approaches. Neurochemical and electrophysiological experiments indicated that 5-HT1Aauto- and 5-HT2A hetero-receptors act in concert to maintain an inhibitory influence on theserotonergic system, particularly in response of escitalopram to increased levels of endogenous 5-HT: the absence of one receptor being compensated by an up-regulation of the other. Finally,SERT knockout mice might be a new model to test the mechanism of escitalopram for anincrease of norephedrine (NE) level.

Bases: A antinocicepção induzida por substâncias doces tem sido largamente estudada. Contudo, a investigação dos neurotransmissores envolvidos nesse processo antinociceptivo ainda carece de mais estudos, pois é de extrema importância entender o envolvimento desses neurotransmissores no sistema neural que controla este tipo de antinocicepção. Objetivo: O objetivo deste estudo é clarificar o envolvimento dos sistemas opióide e serotoninérgico na antinocicepção induzida por substância doce. Método: O presente trabalho foi realizado em modelo animal (Rattus norvegicus, Rodentia, Muridae), objetivando investigar se a ingestão crônica de solução de sacarose é seguida de antinocicepção. A latência de retirada de cauda após a aplicação de estímulo nocivo térmico foi medida antes e após esse tratamento no teste de retirada de cauda (provavelmente um reflexo espinal). Não houve diferenças estatisticamente significantes entre os valores de linha basal dos diferentes grupos e foi calculado um índice de analgesia da latência de retirada de cauda antes e depois do tratamento. O envolvimento de opióides endógenos e de serotonina neste processo antinociceptivo foi pesquisado com fármacos antagonistas específicos e não-específicos dos receptores opióides e serotoninérgicos. Resultados: O efeito analgésico da ingestão de sacarose depende da concentração da solução de sacarose e do tempo de duração do consumo da mesma. Naltrexona e metisergida diminuíram a antinocicepção induzida por substâncias doce (após 14 dias de ingestão da sacarose). Estes efeitos foram corroborados pela administração periférica de naloxonazina e cetanserina. Conclusões: Os resultados sugerem o envolvimento de opióides endógenos e serotonina no processo antinociceptivo atualmente estudado. Tudo apontando para a participação de receptores opióides µ1 e serotoninérgicos 5-HT2 na regulação central da antinocicepção induzida por substâncias doces. / Rationale: Sweet substance-induced antinociception has been widely studied, and the investigation of the neurotransmitters involved in the antinociceptive process is an important way for understanding the involvement of neural system controlling this kind of antinociception. Objective: The aim of this study is to investigate the involvement of opioid and serotonergic system in the sweet substance-induces antinociception. Methods: the present work was made in animal model (Rattus norvegicus, Rodentia, Muridae); with the aim of investigating if the chronic intake of sweet substance, such as sucrose, is followed by antinociception. Their tail withdrawal latencies in the tail-flick test (probably a spinal reflex) were measured before and immediately after this treatment. As there was not statistic significant differences between baseline values of different groups, an analgesia index was calculated from the withdrawal latencies before and after treatment. The involvement of endogenous opioid and serotonin in the antinociceptive process was investigated with specific and non-specific pharmacological antagonism on opioid and serotonergic receptors. Results: The analgesic effect of sucrose intake depends on the concentration of sucrose solution and on the time during which the solution is consumed. Naltrexone and methysergide decreased the sweet substance-induced antinociception (post 14 days of sucrose intake). These effects were corroborated by peripheral administration of naloxonazina and ketanserin. Conclusions: The present results suggest the involvement of endogenous opioids and serotonin in the antinociceptive process presently studied. µ1-opioid and 5-HT2 serotonergic receptors may be involved in the central regulation of the sweet substance-produced antinociception.

Bases: A antinocicepção induzida por substâncias doces tem sido largamente estudada. Contudo, a investigação dos neurotransmissores envolvidos nesse processo antinociceptivo ainda carece de mais estudos, pois é de extrema importância entender o envolvimento desses neurotransmissores no sistema neural que controla este tipo de antinocicepção. Objetivo: O objetivo deste estudo é clarificar o envolvimento dos sistemas opióide e serotoninérgico na antinocicepção induzida por substância doce. Método: O presente trabalho foi realizado em modelo animal (Rattus norvegicus, Rodentia, Muridae), objetivando investigar se a ingestão crônica de solução de sacarose é seguida de antinocicepção. A latência de retirada de cauda após a aplicação de estímulo nocivo térmico foi medida antes e após esse tratamento no teste de retirada de cauda (provavelmente um reflexo espinal). Não houve diferenças estatisticamente significantes entre os valores de linha basal dos diferentes grupos e foi calculado um índice de analgesia da latência de retirada de cauda antes e depois do tratamento. O envolvimento de opióides endógenos e de serotonina neste processo antinociceptivo foi pesquisado com fármacos antagonistas específicos e não-específicos dos receptores opióides e serotoninérgicos. Resultados: O efeito analgésico da ingestão de sacarose depende da concentração da solução de sacarose e do tempo de duração do consumo da mesma. Naltrexona e metisergida diminuíram a antinocicepção induzida por substâncias doce (após 14 dias de ingestão da sacarose). Estes efeitos foram corroborados pela administração periférica de naloxonazina e cetanserina. Conclusões: Os resultados sugerem o envolvimento de opióides endógenos e serotonina no processo antinociceptivo atualmente estudado. Tudo apontando para a participação de receptores opióides µ1 e serotoninérgicos 5-HT2 na regulação central da antinocicepção induzida por substâncias doces. / Rationale: Sweet substance-induced antinociception has been widely studied, and the investigation of the neurotransmitters involved in the antinociceptive process is an important way for understanding the involvement of neural system controlling this kind of antinociception. Objective: The aim of this study is to investigate the involvement of opioid and serotonergic system in the sweet substance-induces antinociception. Methods: the present work was made in animal model (Rattus norvegicus, Rodentia, Muridae); with the aim of investigating if the chronic intake of sweet substance, such as sucrose, is followed by antinociception. Their tail withdrawal latencies in the tail-flick test (probably a spinal reflex) were measured before and immediately after this treatment. As there was not statistic significant differences between baseline values of different groups, an analgesia index was calculated from the withdrawal latencies before and after treatment. The involvement of endogenous opioid and serotonin in the antinociceptive process was investigated with specific and non-specific pharmacological antagonism on opioid and serotonergic receptors. Results: The analgesic effect of sucrose intake depends on the concentration of sucrose solution and on the time during which the solution is consumed. Naltrexone and methysergide decreased the sweet substance-induced antinociception (post 14 days of sucrose intake). These effects were corroborated by peripheral administration of naloxonazina and ketanserin. Conclusions: The present results suggest the involvement of endogenous opioids and serotonin in the antinociceptive process presently studied. µ1-opioid and 5-HT2 serotonergic receptors may be involved in the central regulation of the sweet substance-produced antinociception.