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ABSTRACT The Implications of Chronic Stress on Obesity: Allostatic Load on Body Mass Index (BMI) Classification in the United States, NHANES 2005-2006 INTRODUCTION: In this modern environment, our world is reflecting an exponential increase in not only population, but in body size. Obesity is an overwhelming public health concern among the United States population. Research has shown there is a positive correlation between adiposity and stress. Allostatic load (AL) has been presented to be a consistent measure of chronic stress damage on the body. Yet, there is few studies exemplifying the presence AL on classification of body mass index (BMI). AIM: The aim of this study is to find a relationship between allostatic load (AL) and body mass index (BMI) classification in the United States adult population on a large national scale. This complex interaction can predetermine who among the US population will be at greater risk for excess adiposity following this psychoneuroendocrinology. METHODS: A representative sample size of n=3826 was gathered using NHANES data (2005-2006). Criteria for sample included all United States adults that had numerical values for 10 biomarkers chosen to represent chronic stress damage (allostatic load) along with individual body mass index (BMI). Allostatic load (low, high) and BMI classification (underweight to class III obese) were further categorized on severity and computed in SPSS to find significance between gradients of each variable (α=.05). Cross-sectional analysis and logistical regression (multivariate) were used to further decipher an association between allostatic load and BMI category. RESULTS: A strong positive correlation between allostatic load risk and BMI category was found (p<.001). Also among the variables in the study, significance was found within the strata of age, gender, race, smoking status and poverty income ratio (PIR). Findings show a strong statistically significant relationship between allostatic load and BMI. DISCUSSION: It is imperative to decipher the directional relationship between stress and obesity to provide effective treatment. Understanding the pathology of how stress affects adiposity could open the door for many clinical and public health interventions to eradicate a very preventable outcome. By addressing the effect of chronic stress, a new avenue of prevention can be developed to combat the growing obesity rates in the United States.

The World Health Organization has called stress-related illness “the health epidemic of the 21st century.” While the biochemical pathways associated with the acute stress response are well-characterized, many of the pathways behave differently under conditions of chronic stress. The purpose of this project is to apply high-sensitivity mass spectrometry (MS)-based targeted and untargeted metabolomics approaches to generate new insights into the biochemical processes and pathways associated with the chronic stress response, and potential mechanisms by which chronic stress produces adverse health effects. Chapter 1 describes the application of sets of targeted and untargeted metabolomics approaches to analyze serum samples from a human epigenetic model of chronic stress in order to identify potential targets for further analysis. To test the resulting hypothesis that oxidative stress is a key feature of chronic stress, a new targeted multiple reaction monitoring (MRM)-MS assay was developed for the accurate quantitation of aldehyde products of lipid peroxidation, as described in Chapter 2. In Chapter 3, the validated method for quantitation of malondialdehyde (MDA) was t applied to mouse plasma samples from a model of chronic social defeat stress to determine whether animals exposed to psychosocial stress show increases in oxidative stress. Mouse plasma samples from this model were also analyzed by untargeted metabolomics using Fourier-transform (FT)-MS to identify other important metabolite features, particularly those that overlap with metabolites identified in the human epigenetic model. Analysis of metabolomic data from two very different models of chronic stress supports the consistent detection of a metabolomic phenotype for chronic stress that is characterized by the dysregulation of energy metabolism associated with decreased concentrations of diacyl-phospholipids in blood. Increased blood concentrations of fatty acids, carnitines, acylcarnitines, and ether phospholipids were also observed. In addition to metabolites associated with energy metabolism, chronic stress also significantly influenced metabolites associated with amino acid metabolism and cell death. This characteristic pattern of differences in metabolite concentrations was observed in the plasma of mice exposed to chronic social defeat stress, irrespective of whether or not they displayed outward signs of a chronic stress response; In fact, mice that were “resilient” to the behavioural effects of chronic social defeat stress displayed an exaggerated phenotype over mice that showed depressive-like symptoms following chronic stress exposure. This may suggest that the observed changes in fatty acid composition are protective against stress. However, changes in fatty acid composition are also known to be associated with a wide variety of pathologies including heart disease, neurodegenerative diseases, and mood disorders, so the lipidomic changes associated with chronic stress may also contribute to its health impact. Overall, the results provide further evidence that changes in energy metabolism are a central part of allostatic adaptation to chronic stress. / Graduate / 0487 / csobsey@gmail.com

The incidence of mild blast traumatic brain injuryhas risen due tothe increased use of improvised explosive devices (IEDs) in militaryconflicts. Mild blast TBI (mbTBI) is especially relevant due to its lack of acutely observable symptoms, and to its association with long-term neurodegenerative and neuropsychiatric disorders. Predominantly, TBI patients often suffer from chronic stress, neuropathic pain and headaches, which greatly compromise the health and quality of life of these individuals. Treatments for neuropathic pain have been empirically found and produce little effect in lessening neuropathic pain, likely due to the lack of targeted therapies. This highlights the need for better understanding of the molecular mechanisms underlying neuropathicpain, TBI and chronic stress that could lead to mechanistic therapeutic targets. Oxidative stress is an important mechanism of the pathophysiology of neuropathic pain, TBI and chronic stress. We hypothesize that acrolein, an endogenously formed neurotoxin, is able to stay active in the body for up to 10 days, is involved in the pathophysiology of neuropathic pain in TBI and chronic stress. This study aims to correlate acrolein elevation in the body with neuropathic pain, deepen the understanding of underlying mechanisms of pain in TBI and chronic stress, and mitigate this pain with acrolein scavenging. The ultimate goal of this research is to provide therapies for TBI and chronic stress patients that can eliminate pain and significantly improve their healthand quality of life

A ouabaína (OUA), um inibidor da Na+ ,K+-ATPase, foi identificada como uma substância endógena presente no plasma humano, e parece estar envolvida na resposta ao estresse agudo, em animais e seres humanos. O estresse crônico é um importante fator agravante de doenças psiquiátricas, incluindo depressão e ansiedade. Além disso, problemas cognitivos são cada vez mais reconhecidos como importantes componentes da ansiedade e depressão. Diante disto, o presente trabalho buscou investigar os efeitos da OUA (1,8 <font face = \"symbol\">mg/kg) na hiperatividade do eixo HPA, na neuroinflamação, na expressão de receptores e proteínas envolvidos na plasticidade sináptica, nos efeitos comportamentais (como déficit de memória de longa duração, depressão e ansiedade) e atividade da Na+,K+-ATPase induzidos pelo protocolo de estresse crônico imprevisível (CUS) realizado ao longo de 14 dias em ratos. Nossos resultados demonstraram que o tratamento intermitente com OUA é capaz de reverter a hiperatividade do eixo HPA induzido pelo CUS, por meio da redução de glicocorticoide, redução na expressão de CRH-CRHR1, bem como diminuir a neuroinflamação, e aumentar os níveis de BDNF e fazer o que na expressão dos receptores CRHR2. Essas alterações bioquímicas contribuíram para uma reversão nos prejuízos na memória de longo prazo induzida pelo CUS. Ademais os animais tratados apenas com OUA, bem como os submetidos ao CUS e tratados com OUA obtiveram uma melhora na memória emocional, averiguada no teste comportamental de condicionamento da memória ao medo. Os resultados encontrados sugerem que o protocolo de CUS por 14 dias promove uma adaptação neuronal facilitando a redesignação da memória ao medo, aqui configurado pelo choque, e o tratamento com a OUA abrevia esse processo. Em conclusão os nossos resultados sugerem que o tratamento intermitente com OUA suscita uma adaptação no eixo HPA, por meio de alterações na expressão dos receptores para CRH no hipocampo e hipotálamo, resultando em uma adaptação na memória emocional relacionada ao medo. / Ouabain (OUA), an inhibitor of Na+, K+ -ATPase, has been identified as an endogenous substance present in human plasma, and appears to be involved in the response to acute stress in animals and humans. Chronic stress is an important aggravating factor of psychiatric illness, including depression and anxiety. In addition, cognitive problems are increasingly recognized as important components of anxiety and depression. The present work aimed to investigate the effects of OUA (1.8 <font face = \"symbol\">mg/kg) on HPA axis hyperactivity, neuroinflammation, expression of receptors and proteins involved in synaptic plasticity, behavioral effects (such as long-term memory deficit duration, depression and anxiety) and Na+,K+-ATPase activity induced by the unpredictable chronic stress protocol (CUS) performed over 14 days in rats. Our results demonstrated that intermittent treatment with OUA was able of reversing CUS-induced HPA axis hyperactivity, by reducing glucocorticoid levels, CRH-CRHR1 expression, as well as reducing CUS-induced low-grade neuroinflammation, and increase BDNF levels and expression of CRHR2 receptors. These biochemical changes contributed to a reversal in CUS-induced long-term memory impairment. In addition, animals treated only with OUA, as well as those submitted to CUS, and also treated with OUA obtained an improvement in emotional memory, which was explored in the fear conditioning test. These results suggest that the CUS protocol of 14 days promotes a neural adaptation facilitating a reassignment of the memory to the fear, here configured by the shock, and the treatment with the OUA shortens that process. In conclusion, our results suggest that intermittent treatment with OUA induces an adaptation on the HPA axis, through alterations in the expression of receptors for CRH in the hippocampus and hypothalamus, resulting in an adjustment in fear-related emotional memory.

Made available in DSpace on 2016-04-04T18:29:39Z (GMT). No. of bitstreams: 1 Paulo Eduardo Benzoni.pdf: 990162 bytes, checksum: 2c656c2ab7fb5cf260410fddc0640b12 (MD5) Previous issue date: 2008-02-13 / The stress field has been studied so much where data have demonstrated that in average, more than half of the population of big cities present stress. Stress comes from inner factors (vulnerabilities) and outer ones (environment demands), however, when it is worked on the treatment area itself, it has been observed that some individuals present a sort of persistent behavior which take them to be involved in stressful situations. It is regarded as Lipp nominated: Lives Themes. It is presented on this term a purpose of diagnosis and enlargement of the concept on Lives Themes, grounded on the cognitivebehavioral approach. It was also developed a theorist model of cognitive basis that could explain the problematic of lives themes on chronic stress, such model purposes the individual once attracted by a discriminative stimulus, he activates a scheme which figures out the reality, stirring a sort of inappropriate behavior that takes him to get involved in a stressful situation once there is no appropriate audience of coping , it comes up stress and everything is explained by a belief. Nine participants were evaluated, all of them on chronic stress, where there were five from a physiotherapy clinic-school and others from a psychotherapy private office, all of them under physical and psychological illnesses. They were evaluated through a semi-structured interview, Inventory on Stress Symptoms for adults by Lipp, Inventory of Life and Questionnaires of Schemes by Young. It was made from the purposed theorist model, a model of conceptualization on the Lives Themes, from which all the cases were studied and evaluated. The group s analysis let us to identify the self-sacrifice schemes and inflexible standards as the strongest (hardest) ones and the failure scheme as the weakest one, what enabled to infer that people under chronic stress tend to turn to others, with top-high goals and do not accept failures. It was also observed the presence of factors of behavior and parenthood practices on the development of maladaptative initial schemes which seem to fit the retraced standards of stress, and furthermore, it was also identified the broken (inappropriate) learning of strategies of coping , which turns more difficult the individual under Lives Themes, get rid of this stressful situation, as well as the presence of a discriminative stimulus which stirs the retraced standards of behavior that takes the individual to stressful situations. Finally, it was confirmed the presence of dysfunctional belief that justifies for the individual his situation of being involved constantly in the same stressful situation. The results pointed for the maintenance of the initial hypothesis purposed on the Lives Themes, as well as corroborated for the theorist model purposed. / A ?rea de stress tem sido muito estudada, dados demonstram que em m?dia, mais da metade da popula??o das grandes cidades brasileiras apresentam stress. O stress adv?m de fatores internos (vulnerabilidades) e externos (demandas do ambiente), por?m, quando se trabalha na ?rea de tratamento do mesmo, observa-se que alguns indiv?duos apresentam um padr?o de comportamento persistente que os levam a se envolverem em situa??es estressoras, trata-se do que Lipp denominou de Temas de Vida. Apresenta-se neste trabalho uma proposta de diagn?stico e amplia??o do conceito de temas de vida fundamentada na abordagem cognitivo-comportamental. Desenvolveu-se um modelo te?rico de base cognitiva que pudesse explicar a problem?tica de temas de vida no stress cr?nico, tal modelo prop?e que o indiv?duo atra?do por um est?mulo discriminativo ativa um esquema que interpreta a realidade, acionando um padr?o de comportamento inadequado que o leva a envolver-se na situa??o estressora; n?o havendo repert?rio adequado de coping, surge stress e tudo ? explicado por uma cren?a. Foram avaliados nove participantes, todos com stress cr?nico, sendo cinco de uma cl?nica escola de fisioterapia e quatro de um consult?rio particular de psicoterapia, todos com comorbidades f?sicas e psicol?gicas comuns ao stress cr?nico. Os participantes foram avaliados por meio de entrevista semi-estruturada, Invent?rio de Sintomas de stress para Adultos de Lipp, Invent?rio de Qualidade de Vida e Question?rio de Esquemas de Young. Elaborou-se, a partir do modelo te?rico proposto, um modelo de conceitualiza??o de casos de temas de vida, a partir do qual todos os casos estudados foram avaliados. A analise do grupo permitiu identificar os esquemas de auto-sacrif?cio e padr?es inflex?veis como os mais fortes e o esquema de fracasso como mais fraco o que possibilitou inferir que as pessoas com stress cr?nico tendem a voltar-se aos outros, com metas muito altas e n?o admitem fracasso. Observou-se a presen?a de fatores de temperamento e de pr?ticas parentais no desenvolvimento de esquemas iniciais desadaptativos que parecem modular os padr?es recorrentes de stress observados, al?m disso, identificou-se a aprendizagem inadequada de estrat?gias de coping, que dificultam o indiv?duo com temas de vida sair da situa??o estressora, bem como a presen?a de um est?mulo discriminativo que aciona o padr?o recorrente de comportamento que leva o indiv?duo a situa??es estressoras. Finalmente, confirmou-se a presen?a de uma cren?a disfuncional que justifica para o indiv?duo a sua situa??o de envolver-se constantemente nas mesmas situa??es de stress. Os resultados apontaram para sustenta??o das hip?teses iniciais propostas na teoria de temas de vida, bem como corroboraram o modelo te?rico proposto.

A adolescência é caracterizada como um período de grande estresse na vida humana, sendo o bullying um dos principais estressores desencadeantes de distúrbios psiquiátricos. Modelos animais de depressão usam o estresse social prolongado como indutores de depressão. Utilizamos o modelo de subjugação (ou derrota) social prolongada em camundongos machos adolescentes para estudar a regulação do BDNF neste contexto. Os animais submetidos ao estresse psicossocial apresentaram anedonia no teste de preferência por sacarose e esquiva social no teste de interação social. Explorando a variabilidade comportamental, identificamos grupos suscetíveis e resilientes ao estresse. Animais suscetíveis apresentaram uma redução na expressão do transcrito Bdnf4 e dos níveis proteicos de BDNF total e sua isoforma truncada somente no estriado dorsal, área ainda pouco relacionada à depressão, enquanto que não ocorreram alterações no córtex pré-frontal e hipocampo, áreas comumente afetadas durante a depressão. / Adolescence is characterized by a period of life with great amount of stress, being the bullying one of the main stressors leading to psychiatry disorders. Animal models of depression use prolonged social stress to model depression. We used the prolonged social defeat model in adolescent male mice to study BDNF regulation in this context. Defeated mice showed anhedonia in the sucrose preference test, and social avoidance in the social interaction test. We took advantage of the behavioral outcome variability to identify susceptible and resilient groups to the stress. The susceptible mice showed a reduction in Bdnf4 transcripts, and in total BDNF protein levels, as well as its truncated form in the dorsal striatum, a brain area not much related to depression. However, BDNF gene or protein expression did not differ in the prefrontal cortex and hippocampus, areas commonly associated with depression.

A adolescência é caracterizada como um período de grande estresse na vida humana, sendo o bullying um dos principais estressores desencadeantes de distúrbios psiquiátricos. Modelos animais de depressão usam o estresse social prolongado como indutores de depressão. Utilizamos o modelo de subjugação (ou derrota) social prolongada em camundongos machos adolescentes para estudar a regulação do BDNF neste contexto. Os animais submetidos ao estresse psicossocial apresentaram anedonia no teste de preferência por sacarose e esquiva social no teste de interação social. Explorando a variabilidade comportamental, identificamos grupos suscetíveis e resilientes ao estresse. Animais suscetíveis apresentaram uma redução na expressão do transcrito Bdnf4 e dos níveis proteicos de BDNF total e sua isoforma truncada somente no estriado dorsal, área ainda pouco relacionada à depressão, enquanto que não ocorreram alterações no córtex pré-frontal e hipocampo, áreas comumente afetadas durante a depressão. / Adolescence is characterized by a period of life with great amount of stress, being the bullying one of the main stressors leading to psychiatry disorders. Animal models of depression use prolonged social stress to model depression. We used the prolonged social defeat model in adolescent male mice to study BDNF regulation in this context. Defeated mice showed anhedonia in the sucrose preference test, and social avoidance in the social interaction test. We took advantage of the behavioral outcome variability to identify susceptible and resilient groups to the stress. The susceptible mice showed a reduction in Bdnf4 transcripts, and in total BDNF protein levels, as well as its truncated form in the dorsal striatum, a brain area not much related to depression. However, BDNF gene or protein expression did not differ in the prefrontal cortex and hippocampus, areas commonly associated with depression.

O organismo está sujeito a diversos estímulos estressantes que afetam processos fisiológicos. Embora as alterações de pressão arterial e frequência cardíaca sejam comuns frente à exposição ao estresse, elas podem variar de acordo com os diferentes estressores, tipo de estresse, duração, frequência e intensidade do estímulo aversivo utilizado. O estresse é capaz de alterar em animais a regulação autonômica e reflexos respiratórios, como a atividade do barorreflexo, quimiorreflexo e variabilidade da frequência cardíaca. Além disso, o estresse também é capaz de alterar o comportamento, que são melhorados com o uso de antidepressivos, como a fluoxetina. Nesse sentido, o presente estudo teve como objetivo avaliar se o mesmo tipo de estressor (homotípico) ou diferentes estressores (heterotípico) modulam as respostas cardiovasculares e respiratórias ativadas pelo barorreflexo e quimiorreflexo, respectivamente, além da variabilidade da frequência cardíaca. Além disso, verificar se o tratamento com crônico ou agudo com fluoxetina é capaz de prevenir as alterações ocasionas pelo estresse crônico. Para isto, foram utilizados ratos Wistar, pesando entre 350 a 500g que foram submetidos ao estresse crônico repetido (ECR, homotípico) ou estresse crônico variado (ECV, heterotípico) durante 14 dias consecutivos. Sete dias antes do início dos protocolos de estresse crônico foi iniciado o tratamento com fluoxetina agudo, onde os animais só receberam fluoxetina no dia do experimento ou crônico, em que os animais receberam fluoxetina todos os dias até o dia do experimento, completando 21 dias de tratamento. Os animais ECR e ECV apresentaram uma menor preferência por sacarose, demonstrando comportamento de anedonia, que foi prevenida com o tratamento crônico com fluoxetina. Adicionalmente, ambos os protocolos de estresse demonstraram uma tendência ao aumento nos níveis de corticosterona basais, no entanto os resultados não foram significativos. Ambos os grupos de estresse crônico também apresentaram uma diminuição no peso corporal, entretanto os animais do grupo controle e ECR tratados cronicamente com fluoxetina apresentaram uma diminuição pronunciada do peso corporal quando comparados com seus controles. O ECR aumentou os componentes taquicárdico e bradicárdico do barorreflexo, adicionalmente, o tratamento crônico com fluoxetina preveniu o aumento dos componentes simpático e parassimpático do barorreflexo, porém induziu a redução desses componentes no grupo controle. O tratamento agudo com fluoxetina diminuiu apenas o componente bradicárdico de todos os grupos estressados e controle. Ambos os protocolos de estresse crônico promoveram uma diminuição na modulação simpato-vagal e no ganho do barorreflexo espontâneo, indicando uma hiperatividade simpática, que foi reduzida pelo tratamento crônico e agudo com fluoxetina. Entretanto o tratamento agudo aumentou o número de sequências barorreflexas do tipo UP (aumentos sucessivos de pressão arterial). O ECR e ECV também atenuaram a magnitude da resposta pressora frente à ativação do quimiorreflexo, que foi prevenida com ambos os tratamentos com fluoxetina. Os protocolos de estresse diminuíram os parâmetros basais de ventilação minuto (VE), volume corrente (VT) e aumentou a frequência respiratória (fR), além de aumentar a magnitude da frequência respiratória frente (?fR) a ativação do quimiorreflexo. No mesmo sentido, os tratamentos com fluoxetina aumentaram a magnitude da ?fR, porém apenas o tratamento crônico com fluoxetina preveniu as alterações no parâmetros basais respiratórios de VT e fR. Os achados do presente estudo demonstram que o estresse crônico provoca comportamento do tipo depressivo, além de alterar as respostas autonômicas de barorreflexo e quimiorreflexo e variabilidade cardiocirculatória (PAS e IP), o que pode desencadear patologias no sistema cardiovascular e respiratório. Adicionalmente, nosso trabalho é um dos primeiros a demonstrar que o tratamento crônico com fluoxetina previne a maioria das alterações ocasionadas pelo estresse crônico frente a essas alterações autonômicas / The body is submitted to various stressful stimuli that may affect many physiological processes. Although blood pressure and heart rate oscilations are common during exposure to stress, they can vary according to the different stressors type, duration, frequency and intensity of the aversive stimulus. Several studies suggest that stress can alter the autonomic regulation and respiratory reflexes, such as the baroreflex, chemoreflex activities and heart rate variability. In addition to cardiovascular disorders, chronic stress can also induce behavioral changes that are similar to depression in humans and are reversed by antidepressants, such as fluoxetine. In this way, the present study aimed to assess whether the same type of stressor (homotypic) or different stressors (heterotypic) are able to alter cardiovascular and respiratory responses activated by baroreflex and chemoreflex, respectively. We also aimed to verify the heart rate variability and if the chronic treatment with fluoxetine is able to prevent occasional alterations by chronic stress. For this purpose, male Wistar rats were used, weighing between 350 -500g. They underwent repeated chronic stress (RCS, homotypic) or unpredictable chronic stress (UCS, heterotypic) for 14 consecutive days. Seven days before starting the stress protocols was started the chronic or acute treatment with fluoxetine, until the day of the experiment, completing 21 days of treatment. The RCS and UCS animals have a lower preference for sucrose, demonstrating anhedonia behavior, which was prevented by chronic treatment with fluoxetine. Additionally, both stress protocols showed a tendency to increase basal levels of corticosterone, but the results were not significant. Our results showed that both stress groups have a decrease in body weight, however the control animals and RCS chronically treated with fluoxetine showed a marked decrease in body weight compared to their controls. The RCS increased tachycardia and bradycardia baroreflex components, however chronic treatment with fluoxetine prevented the increase of the sympathetic and parasympathetic components of the baroreflex, but induced a reduction of these components in the control group. Acute treatment with fluoxetine only decreased bradycardic component of all stressed and control groups. Both chronic stress protocols showed a decrease in sympathovagal modulation and spontaneous baroreflex gain, indicating a sympathetic hyperactivity that was decreased by chronic and acute treatment with fluoxetine. Acute fluoxetine treatment increased baroreflexs sequences up. The RCS and UCS also attenuated the magnitude of pressor response, which was prevented by both treatments with fluoxetine. Stress protocols decreased the baseline parameters of VE, VT and increased fR, and increase the magnitude of the respiratory frequency (?fR) by chemoreflex activation. Both treatment with fluoxetine further increased the magnitude of ?fR, but only chronic treatment with fluoxetine prevented the alterations in respiratory baseline parameters VT and fR. The findings of this study demonstrate that chronic stress causes the depressive-like behavior, and change the autonomic responses of baroreflex and chemoreflex and cardiocirculatory variability (PAS and IP), which can trigger diseases in the cardiovascular and respiratory system. In addition, our work is one of the first to show that chronic treatment with fluoxetine prevents most of the changes caused by chronic stress face these autonomic changes

O organismo está sujeito a diversos estímulos estressantes que afetam processos fisiológicos. Embora as alterações de pressão arterial e frequência cardíaca sejam comuns frente à exposição ao estresse, elas podem variar de acordo com os diferentes estressores, tipo de estresse, duração, frequência e intensidade do estímulo aversivo utilizado. O estresse é capaz de alterar em animais a regulação autonômica e reflexos respiratórios, como a atividade do barorreflexo, quimiorreflexo e variabilidade da frequência cardíaca. Além disso, o estresse também é capaz de alterar o comportamento, que são melhorados com o uso de antidepressivos, como a fluoxetina. Nesse sentido, o presente estudo teve como objetivo avaliar se o mesmo tipo de estressor (homotípico) ou diferentes estressores (heterotípico) modulam as respostas cardiovasculares e respiratórias ativadas pelo barorreflexo e quimiorreflexo, respectivamente, além da variabilidade da frequência cardíaca. Além disso, verificar se o tratamento com crônico ou agudo com fluoxetina é capaz de prevenir as alterações ocasionas pelo estresse crônico. Para isto, foram utilizados ratos Wistar, pesando entre 350 a 500g que foram submetidos ao estresse crônico repetido (ECR, homotípico) ou estresse crônico variado (ECV, heterotípico) durante 14 dias consecutivos. Sete dias antes do início dos protocolos de estresse crônico foi iniciado o tratamento com fluoxetina agudo, onde os animais só receberam fluoxetina no dia do experimento ou crônico, em que os animais receberam fluoxetina todos os dias até o dia do experimento, completando 21 dias de tratamento. Os animais ECR e ECV apresentaram uma menor preferência por sacarose, demonstrando comportamento de anedonia, que foi prevenida com o tratamento crônico com fluoxetina. Adicionalmente, ambos os protocolos de estresse demonstraram uma tendência ao aumento nos níveis de corticosterona basais, no entanto os resultados não foram significativos. Ambos os grupos de estresse crônico também apresentaram uma diminuição no peso corporal, entretanto os animais do grupo controle e ECR tratados cronicamente com fluoxetina apresentaram uma diminuição pronunciada do peso corporal quando comparados com seus controles. O ECR aumentou os componentes taquicárdico e bradicárdico do barorreflexo, adicionalmente, o tratamento crônico com fluoxetina preveniu o aumento dos componentes simpático e parassimpático do barorreflexo, porém induziu a redução desses componentes no grupo controle. O tratamento agudo com fluoxetina diminuiu apenas o componente bradicárdico de todos os grupos estressados e controle. Ambos os protocolos de estresse crônico promoveram uma diminuição na modulação simpato-vagal e no ganho do barorreflexo espontâneo, indicando uma hiperatividade simpática, que foi reduzida pelo tratamento crônico e agudo com fluoxetina. Entretanto o tratamento agudo aumentou o número de sequências barorreflexas do tipo UP (aumentos sucessivos de pressão arterial). O ECR e ECV também atenuaram a magnitude da resposta pressora frente à ativação do quimiorreflexo, que foi prevenida com ambos os tratamentos com fluoxetina. Os protocolos de estresse diminuíram os parâmetros basais de ventilação minuto (VE), volume corrente (VT) e aumentou a frequência respiratória (fR), além de aumentar a magnitude da frequência respiratória frente (?fR) a ativação do quimiorreflexo. No mesmo sentido, os tratamentos com fluoxetina aumentaram a magnitude da ?fR, porém apenas o tratamento crônico com fluoxetina preveniu as alterações no parâmetros basais respiratórios de VT e fR. Os achados do presente estudo demonstram que o estresse crônico provoca comportamento do tipo depressivo, além de alterar as respostas autonômicas de barorreflexo e quimiorreflexo e variabilidade cardiocirculatória (PAS e IP), o que pode desencadear patologias no sistema cardiovascular e respiratório. Adicionalmente, nosso trabalho é um dos primeiros a demonstrar que o tratamento crônico com fluoxetina previne a maioria das alterações ocasionadas pelo estresse crônico frente a essas alterações autonômicas / The body is submitted to various stressful stimuli that may affect many physiological processes. Although blood pressure and heart rate oscilations are common during exposure to stress, they can vary according to the different stressors type, duration, frequency and intensity of the aversive stimulus. Several studies suggest that stress can alter the autonomic regulation and respiratory reflexes, such as the baroreflex, chemoreflex activities and heart rate variability. In addition to cardiovascular disorders, chronic stress can also induce behavioral changes that are similar to depression in humans and are reversed by antidepressants, such as fluoxetine. In this way, the present study aimed to assess whether the same type of stressor (homotypic) or different stressors (heterotypic) are able to alter cardiovascular and respiratory responses activated by baroreflex and chemoreflex, respectively. We also aimed to verify the heart rate variability and if the chronic treatment with fluoxetine is able to prevent occasional alterations by chronic stress. For this purpose, male Wistar rats were used, weighing between 350 -500g. They underwent repeated chronic stress (RCS, homotypic) or unpredictable chronic stress (UCS, heterotypic) for 14 consecutive days. Seven days before starting the stress protocols was started the chronic or acute treatment with fluoxetine, until the day of the experiment, completing 21 days of treatment. The RCS and UCS animals have a lower preference for sucrose, demonstrating anhedonia behavior, which was prevented by chronic treatment with fluoxetine. Additionally, both stress protocols showed a tendency to increase basal levels of corticosterone, but the results were not significant. Our results showed that both stress groups have a decrease in body weight, however the control animals and RCS chronically treated with fluoxetine showed a marked decrease in body weight compared to their controls. The RCS increased tachycardia and bradycardia baroreflex components, however chronic treatment with fluoxetine prevented the increase of the sympathetic and parasympathetic components of the baroreflex, but induced a reduction of these components in the control group. Acute treatment with fluoxetine only decreased bradycardic component of all stressed and control groups. Both chronic stress protocols showed a decrease in sympathovagal modulation and spontaneous baroreflex gain, indicating a sympathetic hyperactivity that was decreased by chronic and acute treatment with fluoxetine. Acute fluoxetine treatment increased baroreflexs sequences up. The RCS and UCS also attenuated the magnitude of pressor response, which was prevented by both treatments with fluoxetine. Stress protocols decreased the baseline parameters of VE, VT and increased fR, and increase the magnitude of the respiratory frequency (?fR) by chemoreflex activation. Both treatment with fluoxetine further increased the magnitude of ?fR, but only chronic treatment with fluoxetine prevented the alterations in respiratory baseline parameters VT and fR. The findings of this study demonstrate that chronic stress causes the depressive-like behavior, and change the autonomic responses of baroreflex and chemoreflex and cardiocirculatory variability (PAS and IP), which can trigger diseases in the cardiovascular and respiratory system. In addition, our work is one of the first to show that chronic treatment with fluoxetine prevents most of the changes caused by chronic stress face these autonomic changes