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Disfunção autonômica, inflamação e estresse oxidativo são características da hipertensão. Investigamos a cronologia das adaptações fisiológicas e celulares induzidas pelo treinamento aeróbio em ratos espontaneamente hipertensos (SHR). SHR exibiam disfunção autonômica e, no núcleo Paraventricular no hipotálamo (PVN), estresse oxidativo e inflamação. Duas semanas de treinamento aeróbio normalizaram a função autonômica, estresse oxidativo, inflamação, ativação de microglia e conteúdo de HMGB no PVN. Após 8 semanas, SHR treinados apresentaram menor pressão arterial e resistência vascular periférica. Redução do conteúdo de HMGB1 consiste num mecanismo para explicar os benefícios do treinamento, já que infusão aguda intracerebroventricular de HMGB1 produziu disfunção autonômica e ativação de microglia pela sinalização do CxCr4. Assim, redução do estresse oxidativo e da inflamação induzida pelo treinamento contribui para a reversão da disfunção autonômica na hipertensão e a redução da liberação de HMGB1 explica estes benefícios. / Autonomic dysfunction, inflammation and oxidative stress are hallmarks in hypertension. We evaluated time-course of physiologic and cellular adaptations induced by aerobic training in spontaneous hypertensive rat (SHR). SHR showed autonomic dysfunction and, in the hypothalamic paraventricular nucleus (PVN), oxidative stress and inflammation. 2-weeks of aerobic training normalized autonomic function, oxidative stress, inflammation, microglia activation and HMGB1 content into the PVN. After 8-weeks, trained SHR exhibited lower arterial pressure and peripheral vascular resistance. Decrease of HMGB1 content is a mechanism to explain these training benefits, since HMGB1 intracerebroventricular acute infusion induced autonomic dysfunction, microglia activation through CxCr4 signaling. So, decrease of oxidative stress and inflammation induced by aerobic training contributes to reverse autonomic dysfunction in hypertension and decrease of HMGB1 content explains these benefits.

Morphine withdrawal increases the HPA axis activity, which is dependent on a hyperactivity of noradrenergic pathways (NTS-A2) innervating the PVN. In this Thesis we found that morphine withdrawal resulted in an increase in ACTH and corticosterone secretion and a neuronal activation in the PVN. Additionally, we found robust increases in CRF and AVP hnRNAs in the PVN, concomitantly with an increase in c-Fos expression. Morphine withdrawal activated ERK1/2 in PVN and NTS, which could be involved in the c-Fos expression. Morphine withdrawal induced an increase in TH mRNA levels in the NTS-A2, total TH protein in the NTS and TH phosphorylation at Ser31 in PVN and NTS-A2, which resulted in an augmentation of TH activity in the PVN. The enhancement in TH phosphorylated at Ser31 was blocked by SL327 in both nuclei. Finally, we have found that adrenalectomy eliminated the hyperactivity of noradrenergic pathways innervating the PVN during morphine withdrawal. / La abstinencia a morfina aumenta la actividad del eje HHA, que depende de la hiperactivación de las vías noradrenérgicas (NTS-A2) que inervan al PVN. En esta Tesis encontramos que la abstinencia a morfina induce la liberación de ACTH y corticosterona y la activación neuronal del PVN. Además, observamos un aumento en los niveles de hnRNA para CRF y AVP en el PVN, concomitantemente con un incremento en la expresión de c-Fos. El síndrome de abstinencia a morfina activó a ERK1/2 en PVN y NTS. También indujo un incremento en el mRNA para TH en el NTS-A2, proteína TH total y fosforilación de TH en su Ser31 en PVN y NTS-A2, que se tradujo en un aumento en su actividad enzimática. El aumento de TH fosforilada en Ser31 fue bloqueado por SL327. Finalmente, la adrenalectomía eliminó la hiperactividad de las vías noradrenérgicas que inervan al PVN durante la abstinencia a morfina.

Disfunção autonômica, inflamação e estresse oxidativo são características da hipertensão. Investigamos a cronologia das adaptações fisiológicas e celulares induzidas pelo treinamento aeróbio em ratos espontaneamente hipertensos (SHR). SHR exibiam disfunção autonômica e, no núcleo Paraventricular no hipotálamo (PVN), estresse oxidativo e inflamação. Duas semanas de treinamento aeróbio normalizaram a função autonômica, estresse oxidativo, inflamação, ativação de microglia e conteúdo de HMGB no PVN. Após 8 semanas, SHR treinados apresentaram menor pressão arterial e resistência vascular periférica. Redução do conteúdo de HMGB1 consiste num mecanismo para explicar os benefícios do treinamento, já que infusão aguda intracerebroventricular de HMGB1 produziu disfunção autonômica e ativação de microglia pela sinalização do CxCr4. Assim, redução do estresse oxidativo e da inflamação induzida pelo treinamento contribui para a reversão da disfunção autonômica na hipertensão e a redução da liberação de HMGB1 explica estes benefícios. / Autonomic dysfunction, inflammation and oxidative stress are hallmarks in hypertension. We evaluated time-course of physiologic and cellular adaptations induced by aerobic training in spontaneous hypertensive rat (SHR). SHR showed autonomic dysfunction and, in the hypothalamic paraventricular nucleus (PVN), oxidative stress and inflammation. 2-weeks of aerobic training normalized autonomic function, oxidative stress, inflammation, microglia activation and HMGB1 content into the PVN. After 8-weeks, trained SHR exhibited lower arterial pressure and peripheral vascular resistance. Decrease of HMGB1 content is a mechanism to explain these training benefits, since HMGB1 intracerebroventricular acute infusion induced autonomic dysfunction, microglia activation through CxCr4 signaling. So, decrease of oxidative stress and inflammation induced by aerobic training contributes to reverse autonomic dysfunction in hypertension and decrease of HMGB1 content explains these benefits.

L’obésité provient d’un déséquilibre de l’homéostasie énergétique, c’est-à-dire une augmentation des apports caloriques et/ou une diminution des dépenses énergétiques. Plusieurs données, autant anatomiques que physiologiques, démontrent que l’hypothalamus est un régulateur critique de l’appétit et des dépenses énergétiques. En particulier, le noyau paraventriculaire (noyau PV) de l’hypothalamus intègre plusieurs signaux provenant du système nerveux central (SNC) et/ou de la périphérie, afin de contrôler l’homéostasie énergétique via des projections axonales sur les neurones pré-ganglionnaires du système autonome situé dans le troc cérébral et la moelle épinière. Plusieurs facteurs de transcription, impliqués dans le développement du noyau PV, ont été identifiés. Le facteur de transcription SIM1, qui est produit par virtuellement tous les neurones du noyau PV, est requis pour le développement du noyau PV. En effet, lors d’une étude antérieure, nous avons montré que le noyau PV ne se développe pas chez les souris homozygotes pour un allèle nul de Sim1. Ces souris meurent à la naissance, probablement à cause des anomalies du noyau PV. Par contre, les souris hétérozygotes survivent, mais développent une obésité précoce. De façon intéressante, le noyau PV des souris Sim1+/- est hypodéveloppé, contenant 24% moins de cellules. Ces données suggèrent fortement que ces anomalies du développement pourraient perturber le fonctionnement du noyau PV et contribuer au développement du phénotype d’obésité. Dans ce contexte, nous avons entrepris des travaux expérimentaux ayant pour but d’étudier l’impact de l’haploinsuffisance de Sim1 sur : 1) le développement du noyau PV et de ses projections neuronales efférentes; 2) l’homéostasie énergétique; et 3) les voies neuronales physiologiques contrôlant l’homéostasie énergétique chez les souris Sim1+/-. A cette fin, nous avons utilisé : 1) des injections stéréotaxiques combinées à des techniques d’immunohistochimie afin de déterminer l’impact de l’haploinsuffisance de Sim1 sur le développement du noyau PV et de ses projections neuronales efférentes; 2) le paradigme des apports caloriques pairés, afin de déterminer l’impact de l’haploinsuffisance de Sim1 sur l’homéostasie énergétique; et 3) une approche pharmacologique, c’est-à-dire l’administration intra- cérébroventriculaire (i.c.v.) et/ou intra-péritonéale (i.p.) de peptides anorexigènes, la mélanotane II (MTII), la leptine et la cholécystokinine (CCK), afin de déterminer l’impact de l’haploinsuffisance de Sim1 sur les voies neuronales contrôlant l’homéostasie énergétique. Dans un premier temps, nous avons constaté une diminution de 61% et de 65% de l’expression de l’ARN messager (ARNm) de l’ocytocine (Ot) et de l’arginine-vasopressine (Vp), respectivement, chez les embryons Sim1+/- de 18.5 jours (E18.5). De plus, le nombre de cellules produisant l’OT et la VP est apparu diminué de 84% et 41%, respectivement, chez les souris Sim1+/- adultes. L’analyse du marquage axonal rétrograde des efférences du noyau PV vers le tronc cérébral, en particulier ses projections sur le noyau tractus solitaire (NTS) aussi que le noyau dorsal moteur du nerf vague (X) (DMV), a permis de démontrer une diminution de 74% de ces efférences. Cependant, la composition moléculaire de ces projections neuronales reste inconnue. Nos résultats indiquent que l’haploinsuffisance de Sim1 : i) perturbe spécifiquement le développement des cellules produisant l’OT et la VP; et ii) abolit le développement d’une portion importante des projections du noyau PV sur le tronc cérébral, et notamment ses projections sur le NTS et le DMV. Ces observations soulèvent donc la possibilité que ces anomalies du développement du noyau PV contribuent au phénotype d’hyperphagie des souris Sim1+/-. En second lieu, nous avons observé que la croissance pondérale des souris Sim1+/- et des souris Sim1+/+ n’était pas significativement différente lorsque la quantité de calories présentée aux souris Sim1+/- était la même que celle consommée par les souris Sim1+/+. De plus, l’analyse qualitative et quantitative des tissus adipeux blancs et des tissus adipeux bruns n’a démontré aucune différence significative en ce qui a trait à la taille et à la masse de ces tissus chez les deux groupes. Finalement, au terme de ces expériences, les souris Sim1+/--pairées n’étaient pas différentes des souris Sim1+/+ en ce qui a trait à leur insulinémie et leur contenu en triglycérides du foie et des masses adipeuses, alors que tous ces paramètres étaient augmentés chez les souris Sim1+/- nourries ad libitum. Ces résultats laissent croire que l’hyperphagie, et non une diminution des dépenses énergétiques, est la cause principale de l’obésité des souris Sim1+/-. Par conséquent, ces résultats suggèrent que : i) l’haploinsuffisance de Sim1 est associée à une augmentation de l’apport calorique sans toutefois moduler les dépenses énergétiques; ii) l’existence d’au moins deux voies neuronales issues du noyau PV : l’une qui régule la prise alimentaire et l’autre la thermogénèse; et iii) l’haploinsuffisance de Sim1 affecte spécifiquement la voie neuronale qui régule la prise alimentaire. En dernier lieu, nous avons montré que l’injection de MTII, de leptine ainsi que de CCK induit une diminution significative de la consommation calorique des souris des deux génotypes, Sim1+/+ et Sim1+/-. De fait, la consommation calorique cumulative des souris Sim1+/- et Sim1+/+ est diminuée de 37% et de 51%, respectivement, durant les 4 heures suivant l’administration i.p. de MTII comparativement à l’administration d’une solution saline. Lors de l’administration i.c.v. de la leptine, la consommation calorique cumulative des souris Sim1+/- et Sim1+/+ est diminuée de 47% et de 32%, respectivement. Finalement, l’injection i.p. de CCK diminue la consommation calorique des souris Sim1+/- et Sim1+/+ de 52% et de 36%, respectivement. L’ensemble des résultats suggère ici que l’haploinsuffisance de Sim1 diminue l’activité de certaines voies neuronales régulant l’homéostasie énergétique, et particulièrement de celles qui contrôlent la prise alimentaire. En résumé, ces travaux ont montré que l’haploinsuffisance de Sim1 affecte plusieurs processus du développement au sein du noyau PV. Ces anomalies du développement peuvent conduire à des dysfonctions de certains processus physiologiques distincts régulés par le noyau PV, et notamment de la prise alimentaire, et contribuer ainsi au phénotype d’obésité. Les souris hétérozygotes pour le gène Sim1 représentent donc un modèle animal unique, où l’hyperphagie, et non les dépenses énergétiques, est la principale cause de l’obésité. En conséquence, ces souris pourraient représenter un modèle expérimental intéressant pour l’étude des mécanismes cellulaires et moléculaires en contrôle de la prise alimentaire. / Obesity arises from imbalance of the energy homeostasis processes. Multiple anatomical and physiological evidence demonstrate the involvement of the hypothalamus in the regulation of energy homeostasis, i.e. appetite and energy expenditure. In particular, the paraventricular nucleus (PVN) of the hypothalamus plays a critical role in these important homeostatic processes. The PVN integrates multiple signals that come from the central nervous system and/or the periphery to control energy homeostasis. It regulates these processes through projections to the dorsal vagal complex (DVC), which includes the dorsal motor nucleus of the vagus (X) (DMV) and the adjacent nucleus of the solitary tract (NST), located in the brainstem. A cascade of transcription factors involved in the specification of the PVN neurons has been described. One component of this cascade, the bHLH-PAS transcription factor SIM1, is required for the development of all neurons of the PVN. Mice homozygous for null alleles of Sim1 die shortly after birth, presumably because of the lack of PVN. In contrast, Sim1 heterozygous mice survive but show early-onset obesity. Interestingly, the number of PVN cells is reduced by 24% in Sim1+/- mice, suggesting that developmental defects may cause PVN dysfunction and, thus, contribute to the obesity phenotype. In order to explore this hypothesis, we studied the impact of Sim1 haploinsufficiency on: 1) the development of the PVN and it efferent axonal projections; 2) energy homeostasis; and 3) neuronal pathways regulating energy homeostasis. We used: 1) stereotaxic injections and immunological techniques to determine the impact of Sim1 haploinsufficiency on PVN, and it efferent axonal projections, development; 2) the pair-feeding paradigm to determine the impact of Sim1 haploinsufficiency on energy homeostasis; and 3) intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) injections of pharmacological agents, melanotan II (MTII), leptin and cholecystokinin (CCK), to determine the impact of Sim1 haploinsufficiency on the neuronal pathways regulating energy homeostasis. First, we noted that the expression of oxytocin (Ot) and argenin-vasopressin (Vp) mRNA is reduced by 61% and 65%, respectively, in the PVN of Sim1+/- E18.5 embryos. Furthermore, the number of OT- and VP-producing cells was found to be decreased by 84% and 41%, respectively, in Sim1+/- adult mice. Analysis of the retrograde axonal labelling of PVN neurons after stereotaxic injection of latex beads into the DVC of Sim1+/+ and Sim1+/- mice, showed a 74% reduction of PVN neurons projecting to the DVC. However, the molecular composition of the cells affected by a decrease of Sim1 remains unknown. These results indicate that Sim1 haploinsufficiency: i) specifically interferes with the development of OT- and VP-producing cells; and ii) abolishes the development of a subset of parvocellular neurons that project to the DVC. These observations therefore raise the possibility that developmental defects contribute to the obesity phenotype of Sim1+/- mice. Second, we observed that pair-fed Sim1+/- mice do not gain more weight than littermate controls from 4 to 16 weeks of age. Moreover, qualitative and quantitative analyses showed significant increases of lean and fat mass, with hyperplasia of white adipose tissue and hypertrophy of brown adipose tissue, in Sim1+/- mice, but not in pair-fed animals. Additionally, at 16 weeks of age, insulin levels as well as liver and adipose tissue triglyceride content were not significantly different between Sim1+/+ and Sim1+/- pair-fed, but were significantly increased in Sim1+/- fed ad libitum. These results suggest that hyperphagia is the main if not the sole contributor to the obesity of Sim1+/- mice. They indicate that: i) Sim1 haploinsufficiency affects mainly food intake with no effect on energy expenditure; ii) food intake and energy expenditure are regulated by divergent pathways within the PVN; and iii) Sim1 haploinsufficiency specifically affects the feeding pathway without interfering with the thermogenesis pathway. Third, we found that, in both mice genotype, injection of MTII, leptin or CCK induces a significant decrease in cumulative food intake. In fact, MTII i.p. injection decreases cumulative food intake of Sim1+/- and Sim1+/+ mice by 37% and 51% respectively, when compared to saline injection. Leptin i.c.v. injection reduces cumulative food intake by 47% and 32% in Sim1+/- and Sim1+/+ mice, respectively. Finally, CCK i.p. injection decreases food intake of Sim1+/- and Sim1+/+ mice by 52% and 36%, respectively. All in all, the results of these latter studies suggest that Sim1 haploinsufficiency diminishes the activity of neuronal pathways regulating energy homeostasis, in particular of pathways controlling food intake. In conclusion, our work has shown that Sim1 haploinsufficiency affects several developmental processes of the PVN. These developmental defects may cause the dysfunction of physiological processes regulated by the PVN, including the control of food intake, and thus contribute to the hyperphagic obesity phenotype. Sim1 heterozygous mice represent an interesting animal model of obesity in which hyperphagia is the main, if not the sole mechanism of their obesity. These mice could therefore represent a unique opportunity to investigate cellular and molecular mechanisms in control of food intake.

Obesity is a growing disorder in the United States, affecting over 60% of the population. We previously defined sympathetic nervous system (SNS) outflow from brain to white adipose tissue (WAT) using a viral transneuronal tract tracer. SNS innervation of WAT is the principle initiator of lipolysis, whereas decreases in sympathetic drive promote lipid accumulation. Which of the many origins of SNS outflow from brain to WAT results in SNS-mediated changes in lipid mobilization (increases in drive) or accumulation (decrease in drive) is unknown. Previous research indicates that sympathetic denervation blocks lipid mobilization; thus, rostral sites in the neuroaxis connected to WAT via the SNS may promote WAT lipid mobilization. The hypothalamic paraventricular nucleus (PVN) may play a role via its descending projections to the intermediolateral horn of the spinal cord. Therefore, the consequences of PVN lesions (PVNx) on WAT mobilization or accumulation were tested. PVNx resulted in increased lipid accumulation, indicated by increases in retroperitoneal (RWAT) , epididymal (EWAT) , and inguinal WAT (IWAT) pad masses, in fed hamsters, but PVNx did not block fasting (56 h)-induced lipid mobilization. Because adrenal medullary catecholamines, especially epinephrine, also play a minor role in lipid mobilization, we tested the contribution of catecholamine release on lipid mobilization through adrenal demedullation (ADMEDx), with and without PVNx, and found fastinginduced lipid mobilization was not blocked. There was, however, a suggestion that distal denervation of IWAT, with and without ADMEDx, partially blocked lipid mobilization. In addition, evidence suggests SNS also may be an important controller of fat cell proliferation. Surgical denervation of WAT triggers increases in fat cell number (FCN), but have not determined if this FCN increase is due to preadipocyte proliferation or differentiation of preadipocytes into mature fat cells. We also have not demonstrated what role sensory innervation may have in regulating white adipocyte proliferation. Therefore, the role of WAT sympathetic or sensory innervation on adipocyte proliferation was tested. The SNS but not sensory denervation triggered bona fide proliferation as indicated by bromodeoxyuridine plus AD3, a specific adipocyte membrane protein, colabeling. These and previous data suggest that the SNS plays a role in regulating adiposity.

L’obésité provient d’un déséquilibre de l’homéostasie énergétique, c’est-à-dire une augmentation des apports caloriques et/ou une diminution des dépenses énergétiques. Plusieurs données, autant anatomiques que physiologiques, démontrent que l’hypothalamus est un régulateur critique de l’appétit et des dépenses énergétiques. En particulier, le noyau paraventriculaire (noyau PV) de l’hypothalamus intègre plusieurs signaux provenant du système nerveux central (SNC) et/ou de la périphérie, afin de contrôler l’homéostasie énergétique via des projections axonales sur les neurones pré-ganglionnaires du système autonome situé dans le troc cérébral et la moelle épinière. Plusieurs facteurs de transcription, impliqués dans le développement du noyau PV, ont été identifiés. Le facteur de transcription SIM1, qui est produit par virtuellement tous les neurones du noyau PV, est requis pour le développement du noyau PV. En effet, lors d’une étude antérieure, nous avons montré que le noyau PV ne se développe pas chez les souris homozygotes pour un allèle nul de Sim1. Ces souris meurent à la naissance, probablement à cause des anomalies du noyau PV. Par contre, les souris hétérozygotes survivent, mais développent une obésité précoce. De façon intéressante, le noyau PV des souris Sim1+/- est hypodéveloppé, contenant 24% moins de cellules. Ces données suggèrent fortement que ces anomalies du développement pourraient perturber le fonctionnement du noyau PV et contribuer au développement du phénotype d’obésité. Dans ce contexte, nous avons entrepris des travaux expérimentaux ayant pour but d’étudier l’impact de l’haploinsuffisance de Sim1 sur : 1) le développement du noyau PV et de ses projections neuronales efférentes; 2) l’homéostasie énergétique; et 3) les voies neuronales physiologiques contrôlant l’homéostasie énergétique chez les souris Sim1+/-. A cette fin, nous avons utilisé : 1) des injections stéréotaxiques combinées à des techniques d’immunohistochimie afin de déterminer l’impact de l’haploinsuffisance de Sim1 sur le développement du noyau PV et de ses projections neuronales efférentes; 2) le paradigme des apports caloriques pairés, afin de déterminer l’impact de l’haploinsuffisance de Sim1 sur l’homéostasie énergétique; et 3) une approche pharmacologique, c’est-à-dire l’administration intra- cérébroventriculaire (i.c.v.) et/ou intra-péritonéale (i.p.) de peptides anorexigènes, la mélanotane II (MTII), la leptine et la cholécystokinine (CCK), afin de déterminer l’impact de l’haploinsuffisance de Sim1 sur les voies neuronales contrôlant l’homéostasie énergétique. Dans un premier temps, nous avons constaté une diminution de 61% et de 65% de l’expression de l’ARN messager (ARNm) de l’ocytocine (Ot) et de l’arginine-vasopressine (Vp), respectivement, chez les embryons Sim1+/- de 18.5 jours (E18.5). De plus, le nombre de cellules produisant l’OT et la VP est apparu diminué de 84% et 41%, respectivement, chez les souris Sim1+/- adultes. L’analyse du marquage axonal rétrograde des efférences du noyau PV vers le tronc cérébral, en particulier ses projections sur le noyau tractus solitaire (NTS) aussi que le noyau dorsal moteur du nerf vague (X) (DMV), a permis de démontrer une diminution de 74% de ces efférences. Cependant, la composition moléculaire de ces projections neuronales reste inconnue. Nos résultats indiquent que l’haploinsuffisance de Sim1 : i) perturbe spécifiquement le développement des cellules produisant l’OT et la VP; et ii) abolit le développement d’une portion importante des projections du noyau PV sur le tronc cérébral, et notamment ses projections sur le NTS et le DMV. Ces observations soulèvent donc la possibilité que ces anomalies du développement du noyau PV contribuent au phénotype d’hyperphagie des souris Sim1+/-. En second lieu, nous avons observé que la croissance pondérale des souris Sim1+/- et des souris Sim1+/+ n’était pas significativement différente lorsque la quantité de calories présentée aux souris Sim1+/- était la même que celle consommée par les souris Sim1+/+. De plus, l’analyse qualitative et quantitative des tissus adipeux blancs et des tissus adipeux bruns n’a démontré aucune différence significative en ce qui a trait à la taille et à la masse de ces tissus chez les deux groupes. Finalement, au terme de ces expériences, les souris Sim1+/--pairées n’étaient pas différentes des souris Sim1+/+ en ce qui a trait à leur insulinémie et leur contenu en triglycérides du foie et des masses adipeuses, alors que tous ces paramètres étaient augmentés chez les souris Sim1+/- nourries ad libitum. Ces résultats laissent croire que l’hyperphagie, et non une diminution des dépenses énergétiques, est la cause principale de l’obésité des souris Sim1+/-. Par conséquent, ces résultats suggèrent que : i) l’haploinsuffisance de Sim1 est associée à une augmentation de l’apport calorique sans toutefois moduler les dépenses énergétiques; ii) l’existence d’au moins deux voies neuronales issues du noyau PV : l’une qui régule la prise alimentaire et l’autre la thermogénèse; et iii) l’haploinsuffisance de Sim1 affecte spécifiquement la voie neuronale qui régule la prise alimentaire. En dernier lieu, nous avons montré que l’injection de MTII, de leptine ainsi que de CCK induit une diminution significative de la consommation calorique des souris des deux génotypes, Sim1+/+ et Sim1+/-. De fait, la consommation calorique cumulative des souris Sim1+/- et Sim1+/+ est diminuée de 37% et de 51%, respectivement, durant les 4 heures suivant l’administration i.p. de MTII comparativement à l’administration d’une solution saline. Lors de l’administration i.c.v. de la leptine, la consommation calorique cumulative des souris Sim1+/- et Sim1+/+ est diminuée de 47% et de 32%, respectivement. Finalement, l’injection i.p. de CCK diminue la consommation calorique des souris Sim1+/- et Sim1+/+ de 52% et de 36%, respectivement. L’ensemble des résultats suggère ici que l’haploinsuffisance de Sim1 diminue l’activité de certaines voies neuronales régulant l’homéostasie énergétique, et particulièrement de celles qui contrôlent la prise alimentaire. En résumé, ces travaux ont montré que l’haploinsuffisance de Sim1 affecte plusieurs processus du développement au sein du noyau PV. Ces anomalies du développement peuvent conduire à des dysfonctions de certains processus physiologiques distincts régulés par le noyau PV, et notamment de la prise alimentaire, et contribuer ainsi au phénotype d’obésité. Les souris hétérozygotes pour le gène Sim1 représentent donc un modèle animal unique, où l’hyperphagie, et non les dépenses énergétiques, est la principale cause de l’obésité. En conséquence, ces souris pourraient représenter un modèle expérimental intéressant pour l’étude des mécanismes cellulaires et moléculaires en contrôle de la prise alimentaire. / Obesity arises from imbalance of the energy homeostasis processes. Multiple anatomical and physiological evidence demonstrate the involvement of the hypothalamus in the regulation of energy homeostasis, i.e. appetite and energy expenditure. In particular, the paraventricular nucleus (PVN) of the hypothalamus plays a critical role in these important homeostatic processes. The PVN integrates multiple signals that come from the central nervous system and/or the periphery to control energy homeostasis. It regulates these processes through projections to the dorsal vagal complex (DVC), which includes the dorsal motor nucleus of the vagus (X) (DMV) and the adjacent nucleus of the solitary tract (NST), located in the brainstem. A cascade of transcription factors involved in the specification of the PVN neurons has been described. One component of this cascade, the bHLH-PAS transcription factor SIM1, is required for the development of all neurons of the PVN. Mice homozygous for null alleles of Sim1 die shortly after birth, presumably because of the lack of PVN. In contrast, Sim1 heterozygous mice survive but show early-onset obesity. Interestingly, the number of PVN cells is reduced by 24% in Sim1+/- mice, suggesting that developmental defects may cause PVN dysfunction and, thus, contribute to the obesity phenotype. In order to explore this hypothesis, we studied the impact of Sim1 haploinsufficiency on: 1) the development of the PVN and it efferent axonal projections; 2) energy homeostasis; and 3) neuronal pathways regulating energy homeostasis. We used: 1) stereotaxic injections and immunological techniques to determine the impact of Sim1 haploinsufficiency on PVN, and it efferent axonal projections, development; 2) the pair-feeding paradigm to determine the impact of Sim1 haploinsufficiency on energy homeostasis; and 3) intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) injections of pharmacological agents, melanotan II (MTII), leptin and cholecystokinin (CCK), to determine the impact of Sim1 haploinsufficiency on the neuronal pathways regulating energy homeostasis. First, we noted that the expression of oxytocin (Ot) and argenin-vasopressin (Vp) mRNA is reduced by 61% and 65%, respectively, in the PVN of Sim1+/- E18.5 embryos. Furthermore, the number of OT- and VP-producing cells was found to be decreased by 84% and 41%, respectively, in Sim1+/- adult mice. Analysis of the retrograde axonal labelling of PVN neurons after stereotaxic injection of latex beads into the DVC of Sim1+/+ and Sim1+/- mice, showed a 74% reduction of PVN neurons projecting to the DVC. However, the molecular composition of the cells affected by a decrease of Sim1 remains unknown. These results indicate that Sim1 haploinsufficiency: i) specifically interferes with the development of OT- and VP-producing cells; and ii) abolishes the development of a subset of parvocellular neurons that project to the DVC. These observations therefore raise the possibility that developmental defects contribute to the obesity phenotype of Sim1+/- mice. Second, we observed that pair-fed Sim1+/- mice do not gain more weight than littermate controls from 4 to 16 weeks of age. Moreover, qualitative and quantitative analyses showed significant increases of lean and fat mass, with hyperplasia of white adipose tissue and hypertrophy of brown adipose tissue, in Sim1+/- mice, but not in pair-fed animals. Additionally, at 16 weeks of age, insulin levels as well as liver and adipose tissue triglyceride content were not significantly different between Sim1+/+ and Sim1+/- pair-fed, but were significantly increased in Sim1+/- fed ad libitum. These results suggest that hyperphagia is the main if not the sole contributor to the obesity of Sim1+/- mice. They indicate that: i) Sim1 haploinsufficiency affects mainly food intake with no effect on energy expenditure; ii) food intake and energy expenditure are regulated by divergent pathways within the PVN; and iii) Sim1 haploinsufficiency specifically affects the feeding pathway without interfering with the thermogenesis pathway. Third, we found that, in both mice genotype, injection of MTII, leptin or CCK induces a significant decrease in cumulative food intake. In fact, MTII i.p. injection decreases cumulative food intake of Sim1+/- and Sim1+/+ mice by 37% and 51% respectively, when compared to saline injection. Leptin i.c.v. injection reduces cumulative food intake by 47% and 32% in Sim1+/- and Sim1+/+ mice, respectively. Finally, CCK i.p. injection decreases food intake of Sim1+/- and Sim1+/+ mice by 52% and 36%, respectively. All in all, the results of these latter studies suggest that Sim1 haploinsufficiency diminishes the activity of neuronal pathways regulating energy homeostasis, in particular of pathways controlling food intake. In conclusion, our work has shown that Sim1 haploinsufficiency affects several developmental processes of the PVN. These developmental defects may cause the dysfunction of physiological processes regulated by the PVN, including the control of food intake, and thus contribute to the hyperphagic obesity phenotype. Sim1 heterozygous mice represent an interesting animal model of obesity in which hyperphagia is the main, if not the sole mechanism of their obesity. These mice could therefore represent a unique opportunity to investigate cellular and molecular mechanisms in control of food intake.

La sociabilité de l’homme est un phénomène complexe. Les théories dominantes essayant d'expliquer les mécanismes neurobiologiques de cette sociabilité ont largement impliqué l'ocytocine (OXT), un neuropeptide qui facilite de nombreuses fonctions et comportements sociaux. L'hypothalamus, parmi ses nombreuses fonctions, synthétise et sécrète l’OXT via son noyau supraoptique (SON) et le noyau paraventriculaire (PVN), faisant de lui un candidat intéressant pour comprendre les bases neurales de cette sociabilité. Dans cette thèse, qui combine trois études en imagerie par résonance magnétique (IRM), nous avons examiné 1) les différences anatomiques au sein de l'hypothalamus entre des participants contrôles et des patients autistes; 2) l’activité de l'hypothalamus, et plus spécifiquement des sous-régions hypothalamiques incluant le SON et le PVN, en réponse à des visages portant différents niveaux de sociabilité; 3) les connections fonctionnelles que ces sous-régions hypothalamiques entretiennent avec d'autres réseaux cérébraux. Nos résultats révèlent une spécificité, tant dans leur activité fonctionnelle que dans leurs connections anatomiques, des deux sous-régions hypothalamiques (SON et PVN) en fonction du niveaux de sociabilité. Ce travail de thèse fournit donc non seulement de nouvelles méthodes pour explorer les petites sous-régions hypothalamiques mais confirme également le rôle de l’hypothalamus dans la sociabilité et ses anomalies, apportant ainsi un nouvel éclairage sur l’origine des dysfonctionnements sociaux dans l’autisme et d'autres pathologies. / Human sociality is a complex phenomenon. Prevailing theories attempting to explain the neurobiological mechanisms of human sociality have implicated neuropeptide oxytocin (OXT), which facilitates numerous social functions and behaviors. The hypothalamus, among its many functions, also synthesizes and secretes OXT via its supraoptic nucleus (SON) and the paraventricular nucleus (PVN), making them viable candidates to understand the underpinnings of various social processes. This thesis combines three magnetic resonance imaging (MRI) studies investigating 1) anatomical difference of the hypothalamus between neurotypics and patients with Autism Spectrum Disorders (ASD); 2) functional MRI of the hypothalamus, specifically in hypothalamic subregions containing SON and PVN in response to faces of individuals with varying social significance; 3) functional connectivity of these hypothalamic subregions to other brain networks. Results revealed differential activity of hypothalamic subregions in response to various faces and distinctive patterns of connectivity to other brain areas that are involved in social cognition, as well as anatomical abnormalities of the hypothalamus in ASD. Altogether, the work in this thesis provides novel methods of measuring small hypothalamic subregions and supporting evidence of hypothalamic involvement in social functions that may also shed some light on social dysfunctions in ASD and other pathologies.

Made available in DSpace on 2016-06-02T19:22:46Z (GMT). No. of bitstreams: 1 DissPSV.pdf: 824448 bytes, checksum: ef5a827f5cc75a41cb7ea788f8415605 (MD5) Previous issue date: 2006-04-20 / Universidade Federal de Minas Gerais / Hypothalamic paraventricular nucleus (PVN) has an important role in the hydroeletrolytic balance and it also participates in the regulation of water and sodium intake. Recent researches described the presence of 5-HT1 receptors in the central nervous system, standing out the subtypes 5-HT1A, 5-HT1B, 5-HT1C and 5-HT1D. The receptor 5-HT1A was one of the firsts to be identified and it is found in the somatodendritic and pos-synaptic forms. It has been showed the participation of PVN 5-HT1A receptor in the hydroeletrolytic balance. Therefore, the aim of this study was: a) To investigate the effects of bilateral injections of serotonin (5-HT) in the PVN about water intake induced by water deprivation and water and 1.8% NaCl intake induced by sodium depletion; b) To investigate the effects of 8-OH-DPAT injection, an 5-HT1A agonist, in the PVN about water intake induced by water deprivation and water and 1.8% NaCl intake induced by sodium depletion; c) To investigate the action of pMPPF, an 5-HT1A antagonist, into the PVN on the effects of 5-HT and 8-OH-DPAT on the water and 1.8% NaCl intake. Holtzman rats (280-320 g) were submitted to the implant of cannulas bilaterally in the PVN. For the implant, the animals were adapted to a stereotaxic apparatus. Using the bregma, introduction points of the stainless steel cannulas were identified according to the coordinates: 1.8 mm caudal to bregma, 0.6 mm lateral to the midline and 5.0 mm below dura mater. 5-HT injections (10, 20, 40 and 50 µg/ 0,2 µl) in the PVN reduced the water intake (13.4±2.0; 12.6±1.3; 12.9±1.0 and 9.0±2.9 ml/ 30 min vs. sal: 18.4±0.8 ml/ 30 min, respectively, n = 6-8) and the doses 10 and 20 µg/ 0.2 µl reduced the 1.8% NaCl intake (7.9 ± 3.0 and 9.0 ± 2.1 ml/ 30 min, respectively, vs. sal: 17.7 ± 1.8 ml/ 30 min, n = 7). 8-OH-DPAT injections (1.0, 2.5 and 5.0 µg/ 0.2 µl) in the PVN reduced the water intake (15.4 ± 1.3; 14.8 ± 1.2 and 14.2 ± 0.9 ml/ 120 min vs. sal: 19.1 ± 1.0 ml/ 120 min, n = 10) and the doses 2.5 µg and 5 µg also reduced 1.8% NaCl intake (12.4 ± 2.7 ml/ 60 min vs. sal: 19.3 ± 1.0 ml/ 60 min; 12.2 ± 1.8 ml/ 120 min vs. sal: 20.0 ± 1.0 ml/ 120 min, respectively, n = 9). pMPPF bilateral injections (5-HT1A antagonist) preview to 8-OH-DPAT injections have completely blocked the inhibitory effect over water intake (sal + DPAT: 13.8 ± 1.1 ml/ 90 min vs. pMPPF + DPAT: 16.4 ± 1.1 ml/ 90 min, n = 12) and 1.8% NaCl (sal + DPAT: 11.4 ± 2.9 ml/ 30 min vs. pMPPF + DPAT: 17.6 ± 1.7 ml/ 30 min, n = 8). 5-HT1A antagonist partially reduced the inhibitory effect of 5-HT on water intake induced by water deprivation (sal+5-HT: 5.9±1.6 ml/ 30 min vs. pMPPF+5-HT: 12.3±1.1 ml/ 30 min, n=12) as well as on sodium intake induced by sodium depletion (sal+5-HT: 2.8±1.3 ml/ 30 min vs. pMPPF+5-HT: 12.3±1.9 ml/ 30 min, n=15). Our results demonstrate the presence of serotonergic mechanisms in PVN inhibiting water and sodium intake and also the participation of pos-synaptic 5-HT1A receptors on water intake control induced by water deprivation and on sodium intake induced by sodium depletion, and that this receptor doesn t have a tonic inhibitory effect. This work also showed others subtypes serotonergic PVN receptors participating in the dipsogenesis and natriorexigenesis control. / O núcleo paraventricular do hipotálamo (NPV) tem uma importante participação no controle do balanço hidroeletrolítico estando envolvido também na regulação da ingestão de água e sódio. Pesquisas recentes mostraram a presença de receptores do tipo 5- HT1 no sistema nervoso central, destacando-se os subtipos 5-HT1A, 5-HT1B, 5-HT1C e 5-HT1D. O receptor 5-HT1A foi um dos primeiros a ser identificado e é encontrado nas formas somatodendrítica e pós-sináptica. Estudos anteriores demonstraram o envolvimento dos receptores 5-HT1A do NPV do hipotálamo no controle do equilíbrio hidroeletrolítico. Portanto, os objetivos deste estudo foram: a) investigar os efeitos de injeções bilaterais de serotonina (5-HT) no NPV sobre a ingestão de água induzida por privação hídrica e sobre a ingestão de água e NaCl 1,8% induzida por depleção de sódio; b) investigar os efeitos da injeção de 8-OH-DPAT, agonista 5-HT1A, no NPV sobre a ingestão de água induzida por privação hídrica e sobre a ingestão de água e NaCl 1,8% induzida por depleção de sódio; c) investigar a ação do pMPPF, antagonista 5-HT1A, no NPV sobre os efeitos da 5-HT e do 8- OH-DPAT na ingestão de água e NaCl 1,8%. Ratos Holtzman (280-320 g) foram submetidos ao implante de cânulas bilateralmente no NPV. Utilizando-se o bregma foram determinados os pontos de introdução das cânulas de aço inoxidável conforme as seguintes coordenadas: 1,8 mm caudal ao bregma, 0,6 mm lateral à linha mediana e 5,0 mm abaixo da dura-máter. Os seguintes resultados foram obtidos: Injeções de 5-HT (10, 20, 40 e 50 µg/ 0,2 µl) no NPV reduziram a ingestão de água (13,4±2,0; 12,6±1,3; 12,9±1,0 e 9,0±2,9 ml/ 30 min vs. sal: 18,4±0,8 ml/ 30 min, respectivamente, n = 6-8) e nas doses 10 e 20 µg/ 0,2 µl reduziram a ingestão de NaCl 1,8% (7,9±3,0 e 9,0±2,1 ml/ 30 min, respectivamente, vs. sal:17,7±1,8 ml/ 30 min, n = 7). Injeções de 8-OH-DPAT (1,0; 2,5 e 5,0 µg/ 0,2 µl) no NPV reduziram a ingestão de água (15,4±1,3; 14,8±1,2 e 14,2±0,9 ml/ 120 min, respectivamente, vs. sal: 19,1±1,0 ml/ 120 min, n=10) e nas doses de 2,5 µg e 5 µg reduziram também a ingestão de NaCl 1,8% (12,4±2,7 ml/ 60 min vs. sal: 19,3±1,0 ml/ 60 min; 12,2±1,8 ml/ 120 min vs. sal: 20,2±1,0 ml/ 120 min, respectivamente, n=9). Injeções bilaterais de pMPPF (antagonista 5- HT1A) prévias as injeções de 8-OH-DPAT bloquearam completamente o seu efeito inibitório sobre a ingestão de água (sal+DPAT: 13,8±1,1 ml/ 90 min vs. pMPPF+DPAT: 16,4±1,1 ml/ 90 min, n=12) e NaCl 1,8% (sal+DPAT: 11,4±2,9 ml/ 30 min vs. pMPPF+DPAT: 17,6±1,7 ml/ 30 min, n=8). O antagonista 5-HT1A reduziu parcialmente o efeito inibitório da 5-HT sobre a ingestão de água induzida por privação hídrica (sal+5-HT: 5,9±1,6 ml/ 30 min vs. pMPPF+5-HT: 12,3±1,1 ml/ 30 min, n=12) e sobre a ingestão de sódio induzida por depleção (sal+5-HT: 2,8±1,3 ml/ 30 min vs. pMPPF+5-HT: 12,3±1,9 ml/ 30 min, n=15). O antagonista pMPPF administrado isoladamente no NPV não alterou a ingestão de água e NaCl 1,8%. Esses resultados demonstram a existência de mecanismos serotoninérgicos no NPV do hipotálamo inibitórios da ingestão de água e sódio e a participação dos receptores 5-HT1A póssinápticos no controle da ingestão de água induzida por privação hídrica e ingestão de sódio induzida por depleção de sódio, e que este receptor não possui efeito inibitório tônico sobre estes comportamentos. Foi demonstrado também que outros subtipos de receptores serotoninérgicos do NPV do hipotálamo estão envolvidos no controle da dipsogênese e natriorexigênese.

Indiana University-Purdue University Indianapolis (IUPUI) / Recent studies in anesthetized rats suggest that autonomic effects relating to thermoregulation that are evoked from the preoptic area (POA) may be mediated through activation of neurons in the dorsomedial hypothalamus (DMH). Disinhibition of neurons in the DMH produces not only cardiovascular changes but also increases in plasma adrenocorticotropic hormone (ACTH) and locomotor activity mimicking those evoked by microinjection of muscimol, a GABAA receptor agonist and neuronal inhibitor, into the POA. Therefore, I tested the hypothesis that all of these effects evoked from the POA are mediated through neurons in the DMH by assessing the effect of bilateral microinjection of muscimol into the DMH on the changes evoked by microinjection of muscimol into the POA in conscious rats. In addition, I tested the hypothesis that neurons in the DMH mediate a specific response that is thought to signal through the POA, the activation of the HPA axis evoked by systemic administration of the inflammatory cytokine IL-1β. After injection of vehicle into the DMH, injection of muscimol into the POA elicited marked increases in heart rate, arterial pressure, body temperature, plasma ACTH and locomotor activity and also increased Fos expression in the hypothalamic paraventricular nucleus (PVN), a region known to control the release of ACTH from the adenohypophysis, and the raphe pallidus, a medullary region known to mediate POA-evoked sympathetic responses. Prior microinjection of muscimol into the DMH produced a modest depression of baseline heart rate, arterial pressure, and body temperature but completely abolished all changes evoked from the POA. Microinjection of muscimol just anterior to the DMH had no effect on POA-evoked autonomic and neuroendocrine changes. Inhibition of neuronal activity in the DMH only partially attenuated the increased activity of the HPA axis following systemic injections of IL-1β. Thus, neurons in the DMH mediate a diverse array of physiological and behavioral responses elicited from the POA, suggesting that the POA represents an important source of inhibitory tone to key neurons in the DMH. However, it is clear that the inflammatory cytokine IL-1β must employ other pathways that are DMH-, and possibly POA-, independent to activate the HPA axis.