O padrão respiratório é formado por 3 fases: inspiração, pós-inspiração, e expiração ativa. Os mecanismos neurais de controle respiratório são organizados por um sistema de neurônios localizados no bulbo. Evidências sugerem o envolvimento dos neurônios quimiossensíveis do núcleo retrotrapezóide (RTN) no controle da expiração ativa. Portanto, o objetivo desta dissertação foi esclarecer a existência de uma projeção do RTN para o a região que contém os neurônios pré-motores do grupamento respiratório ventrolateral caudal (cVRG), o fenótipo dos neurônios e os neurotransmissores envolvidos nessa projeção. Utilizaram-se ratos Wistar adultos, submetidos a procedimentos imunoistoquímicos e eletrofisiológicos. Os resultados mostraram evidências anatomofuncionais de projeções excitatórias da região do RTN para o cVRG. Esta projeção está ativa durante uma situação de hipercapnia, mas não envolve neurônios serotoninérgicos da rafe e tem pouco envolvimento dos neurônios quimiossensíveis do RTN. / The eupnoeic pattern of respiration consists of three phases: inspiration, post-inspiration and stage 2 of expiration (E2). The neural mechanisms for respiratory control are carefully organized by neuron system localized into the medulla oblongata and this system is highly sensitive to CO2. Evidences suggest the involvement of chemosensitive neurons of the retrotrapezoid nucleus (RTN) in the control of expiratory activity of the caudal ventral respiratory group (cVRG) (Janczewski e Feldman, 2006a). In this study, investigate the existence of a projection the RTN from cVRG, the phenotype of the neurons and the neurotransmitters involved in this projection. The experiments were performed in adult male Wistar rats, submitted to immunohistochemical and electrophysiological approaches. The results showed anatomofunctional evidences of excitatory projections from RTN to caudal ventral respiratory group region. This pathway is active during hypercapnia, has minimal involvement of Phox2b neurons of RTN and do not involve serotonergic neurons of raphe.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 100-114).

O padrão respiratório é formado por 3 fases: inspiração, pós-inspiração, e expiração ativa. Os mecanismos neurais de controle respiratório são organizados por um sistema de neurônios localizados no bulbo. Evidências sugerem o envolvimento dos neurônios quimiossensíveis do núcleo retrotrapezóide (RTN) no controle da expiração ativa. Portanto, o objetivo desta dissertação foi esclarecer a existência de uma projeção do RTN para o a região que contém os neurônios pré-motores do grupamento respiratório ventrolateral caudal (cVRG), o fenótipo dos neurônios e os neurotransmissores envolvidos nessa projeção. Utilizaram-se ratos Wistar adultos, submetidos a procedimentos imunoistoquímicos e eletrofisiológicos. Os resultados mostraram evidências anatomofuncionais de projeções excitatórias da região do RTN para o cVRG. Esta projeção está ativa durante uma situação de hipercapnia, mas não envolve neurônios serotoninérgicos da rafe e tem pouco envolvimento dos neurônios quimiossensíveis do RTN. / The eupnoeic pattern of respiration consists of three phases: inspiration, post-inspiration and stage 2 of expiration (E2). The neural mechanisms for respiratory control are carefully organized by neuron system localized into the medulla oblongata and this system is highly sensitive to CO2. Evidences suggest the involvement of chemosensitive neurons of the retrotrapezoid nucleus (RTN) in the control of expiratory activity of the caudal ventral respiratory group (cVRG) (Janczewski e Feldman, 2006a). In this study, investigate the existence of a projection the RTN from cVRG, the phenotype of the neurons and the neurotransmitters involved in this projection. The experiments were performed in adult male Wistar rats, submitted to immunohistochemical and electrophysiological approaches. The results showed anatomofunctional evidences of excitatory projections from RTN to caudal ventral respiratory group region. This pathway is active during hypercapnia, has minimal involvement of Phox2b neurons of RTN and do not involve serotonergic neurons of raphe.

Sinorhizobium meliloti is a nitrogen-fixing endosymbiont of the legume Medicago sativa commonly known as alfalfa. It uses flagellar rotation and chemotaxis to seek roots of host plants to inhabit. This symbiosis serves as a great model system for studying biological nitrogen fixation and plant-microbe interactions. Since alfalfa brings enormous economic value to the USA, investments into the knowledge of the chemotaxis process that initiates symbiosis have the ability to mitigate deterioration of the environment and significantly increase food supply. The chemotaxis system in the enteric bacteria Escherichia coli is well studied and has been a great resource to understanding the process in other bacterial systems including our model organism S. meliloti. This dissertation compares and contrasts the chemotaxis features in E. coli and S. meliloti and investigates their molecular functions. Based on the understanding gained so far, we attempt to offer plausible explanations for the underlying mechanisms of the S. meliloti chemotaxis pathway. Chapter 1 describes why biological nitrogen fixation is important for agriculture and the health of our environment. This chapter also sheds light on the symbiotic relationship between alfalfa and S. meliloti, which culminates in the formation of nitrogen fixing nodules. We expound on the chemotaxis systems in E. coli and other bacteria including S. meliloti and Bacillus subtilis. In chapter 2, we compare the distribution of C-terminal pentapeptide-bearing receptors and the adaptation proteins that they tether in E. coli and S. meliloti. The stoichiometry data show that the ratio of pentapeptide-bearing chemoreceptors to chemotaxis protein (Che)R and CheB molecules are approximately 500- and 160-fold higher in S. meliloti than in E. coli, respectively. Since not all chemoreceptors in chemotactic bacteria have and utilize the pentapeptide moiety, we investigated the S. meliloti system and observed a strong interaction between CheR, activated CheB and the isolated pentapeptides via in-vitro binding studies. On the contrary, unmodified CheB showed weak binding to the pentapeptide. Through in-vivo studies, we highlighted the physiological necessity of the pentapeptide for chemotaxis. S. meliloti strains with substitutions of the conserved tryptophan residue to alanine in one or all four pentapeptide-bearing Methyl-accepting Chemotaxis Proteins (MCPs) resulted in diminished or loss of chemotaxis to glycine betaine, lysine, and acetate, ligands sensed by pentapeptide-bearing McpX and pentapeptide-lacking McpU and McpV, respectively. The flexible linker connecting the pentapeptide to the MCPs together with the pentapeptide itself were shown to be functional on pentapeptide-lacking chemoreceptors and provided adaptational assistance to other chemoreceptors that lacked a functional pentapeptide. Based on these results, we concluded that S. meliloti employs a pentapeptide-dependent adaptation system with MCPs possessing a consensus pentapeptide motif (N/D)WE(E/N)F). Finally, we postulated that the higher abundance of CheR and CheB in S. meliloti compared to E. coli compensates for the lower number of pentapeptide-bearing chemoreceptors in the chemosensory array. In chapter 3, we explored the putative phosphatase function of a novel protein, CheT, on phosphorylated S. meliloti response regulators. The kinase CheA phosphorylates both the sink response regulator, CheY1, and the flagellar motor interacting response regulator, CheY2. CheY1 competes with CheY2 for these phosphate groups, but we have discovered another layer of complexity to the story. Sequence comparison of S. meliloti CheT and the E. coli phosphatase CheZ shows little sequence homology. However, both proteins share a DXXXQ phosphatase motif. Phosphorylation assays performed using radiolabeled [γ-32P]-ATP revealed that CheT acts as a phosphatase of CheY1~P and accelerates dephosphorylation of CheY1~P by at least two-fold. Interestingly, we also discovered that CheT interacts with CheR, but this interaction did not affect the enzymatic activity of either protein under the examined conditions. Unexpectedly, a cheT deletion strain and strains carrying mutations in the phosphatase motif exhibit an increased swimming speed, a phenotype that does not conform with the model that the absence of CheT or its activity results in increased CheY2~P levels and reduced swimming speed. We concluded that a revised S. meliloti signal termination pathway should include CheT enhancing dephosphorylation of CheY1~P and sensory adaptation involving the yet unknown function of CheT on CheR. While the adaptation system in S. meliloti is unexplored, this work provides first insights into fascinating deviations and similarities to the known paradigm. We have also delivered evidence that the S. meliloti signal termination system requires a dedicated phosphatase. The knowledge gained here takes us a step closer to enhance the S. meliloti chemotaxis pathway towards improved symbiosis with alfalfa and to reduce our dependence on environmentally deleterious synthetic fertilizers. / Doctor of Philosophy / Like all living things, bacteria inhabit a constantly changing environment, hence the need to take up and process this information. Bacterial cells have evolved sophisticated biological tools to tackle this challenge of detecting, responding and adapting to environmental signals like nutrients, toxins, temperature changes, light, metabolites, etc. Motile bacteria such as Escherichia coli, a gut resident microbe, and Sinorhizobium meliloti, a soil dwelling bacterium, direct their swimming behavior in response to chemical gradients within the milieu through a process termed chemotaxis. Generally, this vital process enables a bacterium to escape harmful chemicals and gravitate towards beneficial ones. However, S. meliloti specifically employs chemotaxis to locate the roots of its plant host (alfalfa) and to establish a symbiotic relationship through which the bacteria provide essential nitrogen for plant growth in exchange for nourishment. The biological tools employed by S. meliloti for chemotaxis include environmental sensing receptors called Methyl-accepting Chemotaxis Proteins (MCPs) and proteins inside the bacterial cell that transfer information from the sensors to long, helical rotating propeller structures, called flagella. Importantly, the efficiency of this process hinges on a timely termination of information flow and the ability to adapt to prevailing stimuli while maintaining sensitivity to increasing concentration gradients. This work investigates the function of the C-terminal five amino acid motif of MCPs known to be critical for adaptation in E. coli and the phosphatase activity of a novel protein, CheT, in signal termination of S. meliloti chemotaxis system.

A insuficiência cardíaca (IC) é o estágio final de diversas patologias cardíacas e apresenta alta morbimortalidade. Dentre as causas, estão os efeitos cardiotóxicos em pacientes tratados com doxorrubicina (Dox). A fisiopatologia da IC apresenta aumento da atividade barorreflexa e marcada hiperatividade simpática (HS), estado compensatório à redução do débito cardíaco. Porém, a HS prolongada culmina em alterações deletérias para o sistema cardiovascular (SC) com piora do quadro de sintomas. Atualmente muito se discute sobre o papel dos corpúsculos carotídeos (CC) na fisiopatologia da IC devido ao seu reflexo simpatotônico e a melhora de pacientes portadores de IC após a remoção dos CC. O nosso objetivo foi avaliar a influência do CC na evolução da IC induzida pela DOX. Para tal, 35 ratos Wistar machos foram dispostos em 4 grupos: controle Salina (CSAL; n=7) e Controle Dox (CDOX; n=12), Desnervado Salina (DSAL; n=4) e Desnervado Doxo (DDOX; n=12). A desnervação consistiu na ressecção do nervo sinusal bilateral prévia à administração de Dox; a indução da IC ocorreu através de 6 aplicações de Dox, na dose de 2.5mg/kg, pela via IP a cada 4 dias. Após 15 dias do término da indução, os animais foram avaliados pelo ecocardiograma e canulados para registro de pressão arterial invasiva e avaliação hemodinâmica, autonômica, barorreflexa e quimiorreflexa. A análise dos resultados mostra que o grupo CDOX apresentou redução do peso corporal, da sensibilidade baro e quimiorreflexa, hiperatividade simpática acompanhada de redução vagal, redução da morfologia cardíaca associada à disfunção diastólica e sistólica e redução do peso bruto cardíaco e ventricular. A desnervação não foi capaz de reverter os efeitos deletérios causados pela Dox, inclusive a desnervação acentuou a disfunção diastólica e sistólica induzida pela Dox. Concluiu-se que a desnervação carotídea não foi eficiente em melhorar a insuficiência cardíaca induzida pela Dox no modelo experimental proposto / Heart failure (HF) is the final stage of several cardiac pathologies and results in high morbimortality. Among the causes, we can mention the cardiotoxic effects in patients treated with doxorubicin (Dox). The pathophysiology of HF has increased baroreflex activity and marked sympathetic hyperactivity (HS), a compensatory state to the reduction of cardiac output. However, prolonged HS results in worsening of the symptoms. Currently, the role of carotid corpuscles (CC) in the pathophysiology of HF is discussed due improvement of sympathetic reflex presents in patients with HF after CC removal. The objective of this study was to evaluate the influence of CC on the evolution of HF induced by DOX for this method 35 Male Wistar rats arranged in 4 groups: Salina control (CSAL; n = 7) and Dox Control (CDOX; n = 12) Salina Denerved (DSAL; n = 4) and Dox Denerved (DDOX; n = 12). A denervation consisted of bilateral sinus nerve resection prior to Dox administration, induction of HF through 6 Dox applications at a dose of 2.5mg / kg, via IP every 4 days. After 15 days of the end of the induction, the animals were evaluated by echocardiogram and cannulated to record invasive blood pressure and hemodynamic, autonomic, baroreflex and chemorreflex evaluation. Our experiment demonstrated that the CDOX group had reduction of body weight, baro and chemoreflex sensitivity, sympathetic hyperactivity accompanied by vagal reduction, reduction of cardiac morphology associated with diastolic and systolic dysfunction and reduction of gross cardiac and ventricular weight. The denervation is not able to reverse the deleterious effects caused by Dox, including denervation accentuated by Dox-induced diastolic and systolic dysfunction. Based on our results on a carotid denervation it was not effective in improving heart failure induced by Dox

A insuficiência cardíaca (IC) é o estágio final de diversas patologias cardíacas e apresenta alta morbimortalidade. Dentre as causas, estão os efeitos cardiotóxicos em pacientes tratados com doxorrubicina (Dox). A fisiopatologia da IC apresenta aumento da atividade barorreflexa e marcada hiperatividade simpática (HS), estado compensatório à redução do débito cardíaco. Porém, a HS prolongada culmina em alterações deletérias para o sistema cardiovascular (SC) com piora do quadro de sintomas. Atualmente muito se discute sobre o papel dos corpúsculos carotídeos (CC) na fisiopatologia da IC devido ao seu reflexo simpatotônico e a melhora de pacientes portadores de IC após a remoção dos CC. O nosso objetivo foi avaliar a influência do CC na evolução da IC induzida pela DOX. Para tal, 35 ratos Wistar machos foram dispostos em 4 grupos: controle Salina (CSAL; n=7) e Controle Dox (CDOX; n=12), Desnervado Salina (DSAL; n=4) e Desnervado Doxo (DDOX; n=12). A desnervação consistiu na ressecção do nervo sinusal bilateral prévia à administração de Dox; a indução da IC ocorreu através de 6 aplicações de Dox, na dose de 2.5mg/kg, pela via IP a cada 4 dias. Após 15 dias do término da indução, os animais foram avaliados pelo ecocardiograma e canulados para registro de pressão arterial invasiva e avaliação hemodinâmica, autonômica, barorreflexa e quimiorreflexa. A análise dos resultados mostra que o grupo CDOX apresentou redução do peso corporal, da sensibilidade baro e quimiorreflexa, hiperatividade simpática acompanhada de redução vagal, redução da morfologia cardíaca associada à disfunção diastólica e sistólica e redução do peso bruto cardíaco e ventricular. A desnervação não foi capaz de reverter os efeitos deletérios causados pela Dox, inclusive a desnervação acentuou a disfunção diastólica e sistólica induzida pela Dox. Concluiu-se que a desnervação carotídea não foi eficiente em melhorar a insuficiência cardíaca induzida pela Dox no modelo experimental proposto / Heart failure (HF) is the final stage of several cardiac pathologies and results in high morbimortality. Among the causes, we can mention the cardiotoxic effects in patients treated with doxorubicin (Dox). The pathophysiology of HF has increased baroreflex activity and marked sympathetic hyperactivity (HS), a compensatory state to the reduction of cardiac output. However, prolonged HS results in worsening of the symptoms. Currently, the role of carotid corpuscles (CC) in the pathophysiology of HF is discussed due improvement of sympathetic reflex presents in patients with HF after CC removal. The objective of this study was to evaluate the influence of CC on the evolution of HF induced by DOX for this method 35 Male Wistar rats arranged in 4 groups: Salina control (CSAL; n = 7) and Dox Control (CDOX; n = 12) Salina Denerved (DSAL; n = 4) and Dox Denerved (DDOX; n = 12). A denervation consisted of bilateral sinus nerve resection prior to Dox administration, induction of HF through 6 Dox applications at a dose of 2.5mg / kg, via IP every 4 days. After 15 days of the end of the induction, the animals were evaluated by echocardiogram and cannulated to record invasive blood pressure and hemodynamic, autonomic, baroreflex and chemorreflex evaluation. Our experiment demonstrated that the CDOX group had reduction of body weight, baro and chemoreflex sensitivity, sympathetic hyperactivity accompanied by vagal reduction, reduction of cardiac morphology associated with diastolic and systolic dysfunction and reduction of gross cardiac and ventricular weight. The denervation is not able to reverse the deleterious effects caused by Dox, including denervation accentuated by Dox-induced diastolic and systolic dysfunction. Based on our results on a carotid denervation it was not effective in improving heart failure induced by Dox

<p>Aortic bodies (ABs) are putative peripheral arterial chemoreceptors located near the aortic arch. They are hypothesized to contribute to O₂ homeostasis by sensing arterial O₂ content and initiating cardiovascular reflexes during hypoxia; however, information on their cellular physiology is lacking. The primary goal of this thesis was to elucidate chemosensory mechanisms among mammalian (rat) AB cells, located specifically at the bifurcation of the left vagus nerve and recurrent laryngeal nerve (RLN), where they are found in association with a group of local neurons (>30). In vagus nerve-RLN whole-mounts, AB chemoreceptor (type I) cells were immunoreactive against the vesicular acetylcholine (ACh) transporter, and were surrounded by nerve terminals immunopositive for purinergic P2X2 and P2X3 receptor subunits, suggesting that ACh and ATP may act as neurotransmitters as in the related carotid body. In a novel dissociated AB culture model, subsets of type I cells exhibited elevated intracellular Ca²⁺ responses to hypoxia, isohydric hypercapnia, isocapnic acidosis, and acidic hypercapnia, demonstrating their direct chemosensitivity for the first time. Interestingly, surviving local neurons also responded to these chemostimuli, suggesting that they are sensory. Patch clamp electrophysiological and Ca²⁺ imaging studies revealed functional heteromeric P2X2/3 and nicotinic ACh receptors on local neurons, consistent with ACh and/or ATP mediating chemotransmission between receptor cells and local neurons. These neurons were also found to be interconnected by electrical synapses. Finally, the short-term survival of red blood cells (RBCs) in AB cultures, along with the finding that blood-borne factors (e.g. ATP released from RBCs) may have access to AB nerve terminals <em>in situ</em>, implicates RBCs as O₂-sensors in AB function. Altogether, these results suggest an important role for purinergic P2X2/3 receptors on local neurons/nerve terminals and ATP release from type I cells and RBCs, in the unique ability of ABs to sense and process information about blood O₂ content.</p> / Doctor of Philosophy (PhD)

A hiperatividade simpática é uma característica marcante da insuficiência cardíaca (IC). Estudos apontam alterações na sensibilidade quimiorreflexa como um mecanismo potencial para essa alteração autonômica. Por outro lado, sabe-se que o treinamento aeróbico e o treinamento muscular respiratório reduzem a atividade nervosa simpática muscular (ANSM). Objetivo: Neste estudo nós testamos as seguintes hipóteses: 1) o treinamento respiratório combinado ao treinamento aeróbico potencializa a melhora na ANSM, no fluxo sanguíneo muscular (FSM) e na força muscular respiratória, em pacientes com IC; 2) o treinamento respiratório e o treinamento aeróbico melhoram o controle quimiorreflexo da ANSM. Métodos: Foram incluídos pacientes com idade entre 30 e 70 anos, fração de ejeção do ventrículo esquerdo <= 40% e classe funcional II/III (NYHA). Os pacientes foram randomizados em 4 grupos: 1) controle (não treinado, n=10), 2) treinamento respiratório (n=11), 3) treinamento aeróbico (n=9) e 4) treinamento combinado (respiratório + aeróbico, n=9). A ANSM foi avaliada pela técnica de microneurografia e o FSM pela técnica de pletismografia de oclusão venosa. O controle quimiorreflexo periférico foi avaliado pela inalação de mistura gasosa hipóxica (10% de O2 e 90% N2) e o controle quimiorreflexo central pela inalação de mistura gasosa hipercapnica (7% CO2 e 93% O2). A capacidade funcional foi avaliada pelo teste cardiopulmonar. A força muscular respiratória foi avaliada pela pressão inspiratória máxima (PI Máx) e pelas pressões esofágica, gástrica e transdiafragmática. A qualidade de vida foi avaliada pelo questionário de Minessota. O treinamento aeróbico de moderada intensidade teve duração de 40 minutos, 3 vezes por semana, durante 4 meses. O treinamento respiratório consistiu em treinamento muscular inspiratório com carga de 60% da PI Máx, 30 minutos por dia, 5 dias por semana durante 4 meses. Resultados: Os treinos respiratório, aeróbico e combinado diminuíram a ANSM e aumentaram o FSM em repouso. A comparação entre os grupos não mostrou diferenças de respostas entre os grupos treinados. Os treinamentos aeróbico e combinado aumentaram a capacidade funcional (VO2 pico e carga pico). A PI Máx foi maior nos pacientes submetidos ao treinamento respiratório e combinado. A qualidade de vida melhorou nos 3 grupos treinados. O treino aeróbico e o treino respiratório reduziram a resposta de ANSM durante a estimulação dos quimiorreceptores periféricos. Não foram observadas alterações no grupo controle. Conclusão: Ambos, o treinamento respiratório e o treinamento aeróbico, melhoram o controle neurovascular em repouso. Contudo, o treinamento respiratório combinado ao treinamento aeróbico não causa benefício adicional no controle neurovascular, em pacientes com IC. O treinamento respiratório e o treinamento respiratório melhoram a resposta de ANSM à estimulação dos quimiorreceptores periféricos / Introduction: Sympathetic hyperactivity is a hallmark of heart failure (HF). Studies indicate that changes in chemoreflex sensitivity as a potential mechanism for this autonomic alteration. On the other hand, it is known that aerobic training and respiratory muscle training reduce muscular sympathetic nerve activity (MSNA). Objective: In this study we tested the following hypotheses: 1) combined respiratory training and aerobic training promove a more pronuciate effect on MSNA, muscle blood flow (MBF) and respiratory muscle strength in HF patients; 2) respiratory training and aerobic training improve chemorreflex control of MSNA. Methods: Patients aged 30 to 70 years, left ventricular ejection fraction <= 40% and functional class II / III (NYHA) were included. Patients were randomized into 4 groups: 1) control (Untrained, n = 10), 2) respiratory training (n = 11), 3) aerobic training (n = 9) and 4) combined training (n= 9). The MSNA was evaluated by the microneurography technique and the MBF by the venous occlusion plethysmography technique. Peripheral chemoreflex control was evaluated by inhaling hypoxic gas mixture (10% O2 and 90% N2) and the central chemoreflex control by inhaling the hypercapnic gas mixture (7% CO2 and 93% O2). The functional capacity was evaluated by the cardiopulmonary test. Respiratory muscle strength was assessed by maximal inspiratory pressure (PI Max) and by esophageal, gastric and transdiaphragmatic pressure. Quality of life was assessed by the Minnesota Questionnaire. Aerobic training was conducted for four months, 3 times per week, for 40 min at moderate intensity. Respiratory training consisted of inspiratory muscle training for four months, 5 times per week for 30 min, at 60% of PI Max. Results: Respiratory, aerobic and combined training reduced the MSNA and increased the MBF at rest. The comparison between the groups did not show differences of responses among the trained groups. Aerobic and combined training increased functional capacity (peak VO2 and peak load). PI Max was higher in patients submitted to combined and respiratory training. Quality of life improved in the 3 trained groups. Aerobic training and respiratory training reduced the MSNA response during stimulation of peripheral chemoreceptors. No changes were observed in the control group. Conclusion: Both respiratory training and aerobic training improve neurovascular control at rest. However, respiratory training combined with aerobic training does not cause additional benefit in neurovascular control in patients with systolic HF. Respiratory training and respiratory training improve the MSNA response to stimulation of peripheral chemoreceptors

Introdução: Os distúrbios respiratórios do sono são comuns em pacientes com insuficiência cardíaca. Estudos recentes mostram que pacientes com insuficiência cardíaca apresentam resposta vasoconstritora muscular paradoxal durante a estimulação dos quimiorreceptores centrais e periféricos e que essa resposta está associada à disfunção endotelial e à exacerbação nervosa simpática. Porém, o que não se conhece é se essa resposta está intensificada em pacientes com a coexistência de insuficiência cardíaca e distúrbio respiratório do sono. Objetivos: Testar a hipótese de que: 1) A resposta de fluxo sanguíneo muscular (FSM) durante a hipercapnia e a hipóxia seria menor em pacientes com insuficiência cardíaca e distúrbio respiratório do sono que em pacientes com insuficiência cardíaca sem distúrbio respiratório do sono; e 2) A resposta vasoconstritora mais exacerbada em pacientes com a coexistência de insuficiência cardíaca e distúrbio respiratório do sono estaria associada à disfunção endotelial e/ou à resposta exagerada da atividade nervosa simpática muscular (ANSM). Métodos: Foram avaliados, consecutivamente, 90 pacientes com insuficiência cardíaca, classe funcional II-III (New York Heart Association). Destes, 41 preencheram os critérios de inclusão e, após o exame de polissonografia, foram alocados em dois grupos, de acordo com o índice de apneia e hipopneia (IAH): Grupo IC (IAH < 15 eventos/hora; n=13; 46 (39-53) anos) e Grupo IC+DRS (IAH >= 15 eventos/hora; n=28; 57 (54-61) anos). O consumo de oxigênio no pico do exercício ( 2 pico) e a fração de ejeção do ventrículo esquerdo (FEVE) foram avaliados pelo teste cardiopulmonar em esforço e pela ecocardiografia transtorácica basal, respectivamente. Os FSM do antebraço e da panturrilha (FSMab e FSMp, respectivamente) foram avaliados pela pletismografia de oclusão venosa e a ANSM pela técnica de microneurografia. A pressão arterial média (PAM) e a frequência cardíaca (FC) foram avaliadas batimento a batimento de forma não invasiva (Finometer® PRO). O quimiorreflexo central foi estimulado por meio da inalação de uma mistura gasosa hipercápnica (7% CO2 e 93% O2) e o quimiorreflexo periférico por meio da inalação de uma mistura gasosa hipóxica (10% O2 e 90% N2), com isocapnia mantida, durante 3 minutos. Resultados: Os grupos foram semelhantes em relação à etiologia da insuficiência cardíaca 2 pico, índice de massa corpórea e medicações. No basal, não houve diferença entre os grupos quanto ao FSMab e FSMp, condutância vascular do antebraço (CVab) e panturrilha (CVp). Entretanto, a ANSM foi maior no grupo IC+DRS (P<0,05). Durante a hipercapnia, as respostas vasculares (FSMab, CVab, FSMp, CVp) foram significativamente menores no grupo IC+DRS quando comparadas com o grupo IC (P<0,001, para todas as comparações). De forma semelhante, durante a hipóxia, as respostas vasculares (FSMab, CVab, FSMp, CVp) foram significativamente menores no grupo IC+DRS quando comparadas com o grupo IC (P<=0,001, para todas as comparações). A ANSM, em resposta à hipercapnia e à hipóxia, foi maior no grupo IC+DRS. Durante a hipercapnia, as respostas de FC e PAM não foram diferentes entre os grupos. Durante a hipóxia, as respostas de FC não foram diferentes entre os grupos, enquanto a resposta de PAM foi maior nos pacientes do grupo IC+DRS. Não houve diferença na resposta ventilatória entre os grupos estudados. Conclusão: Pacientes com a coexistência de insuficiência cardíaca e distúrbio respiratório do sono apresentam vasoconstrição muscular paradoxal mais exacerbada que pacientes sem o distúrbio respiratório do sono, durante a hipercapnia e a hipóxia, o que parece estar associada, pelo menos em parte, à maior resposta de ANSM / Background: Sleep disordered breathing is common in heart failure patients. Recent studies show that patients with heart failure have paradox muscle vasoconstriction during the central and peripheral chemoreceptors stimulation, which is associated with endothelial dysfunction and exaggerated sympathetic nerve activity. However, whether this vascular response is more pronounced in patients with the coexistence of heart failure and sleep disordered breathing is unknown. Objectives: To test the hypothesis that: 1) The muscle vasoconstriction responses to hypercapnia and hypoxia would be more pronounced in heart failure patients with sleep disordered breathing than in heart failure patients without sleep disordered breathing; 2) This alteration in vascular responses would be associated with endothelial dysfunction and/or exaggerated muscle sympathetic nerve activity (MSNA) responses. Methods: Ninety consecutive heart failure patients, functional class II-III (New York Heart Association), were screened for the study. Forty-one patients who fulfilled all the inclusion criteria were enrolled and allocated into two groups according to apnea-hypopnea index (AHI): HF (AIH < v15 events/hour; n=13, 46 (39-53) years) and HF+SDB (AIH >=15 events/hour; n=28, 57 (54-61) years). Peak oxygen uptake (Peak 2) and left ventricular ejection fraction (LVEF) were evaluated by maximal incremental exercise test and by echocardiography, respectively. Forearm and calf blood flow (FBF and CBF, respectively) were evaluated by venous occlusion plethysmography and MSNA by microneurography technique. Mean blood pressure (MBP) and heart rate (HR) were evaluated by beat-to-beat noninvasive technique (Finometer® PRO). Central chemoreceptors were stimulated by inhalation of a hipercapnic gas mixture (7% CO2 and 93% O2) and peripheral chemoreceptors by inhalation of a hypoxic gas mixture (10% O2 and 90% N2), with maintenance of isocapnia, for 3 minutes each one. Results: Both groups were similar regarding to heart failure etiology, LVEF, Peak 2, body mass index, and medications. At baseline, there were no differences in FBF and CBF, forearm and calf vascular conductance (FVC and CVC, respectively) between groups. However, the MSNA was greater in HF+SDB group (P < 0.05). During hipercapnia, the vascular responses (FBF, FVC, CBF, CVC) were lower in HF+SDB group when compared to HF group (P < 0.001, to all comparisions). Similarly, during hypoxia, the vascular responses (FBF, FVC, CBF, CVC) were lower in HF+SDB group when compared to HF group (P <= 0.001, to all comparisions). The MSNA in response to hypercapnia and hypoxia was greater in HF+SDB group. During hypercapnia, the HR and MBP responses were not different between groups. During hypoxia, the HR responses were similar between groups, while the MBP responses were greater in HF+SDB group. There was no difference in ventilatory response between groups. Conclusion: Patients with the coexistence of heart failure and sleep disordered breathing have more intense muscle vasoconstriction than patients without sleep disordered breathing, during hypercapnia and hypoxia, which seems to be due, at least in part, to increased responsiveness of MSNA

A hiperatividade simpática é uma característica marcante da insuficiência cardíaca (IC). Estudos apontam alterações na sensibilidade quimiorreflexa como um mecanismo potencial para essa alteração autonômica. Por outro lado, sabe-se que o treinamento aeróbico e o treinamento muscular respiratório reduzem a atividade nervosa simpática muscular (ANSM). Objetivo: Neste estudo nós testamos as seguintes hipóteses: 1) o treinamento respiratório combinado ao treinamento aeróbico potencializa a melhora na ANSM, no fluxo sanguíneo muscular (FSM) e na força muscular respiratória, em pacientes com IC; 2) o treinamento respiratório e o treinamento aeróbico melhoram o controle quimiorreflexo da ANSM. Métodos: Foram incluídos pacientes com idade entre 30 e 70 anos, fração de ejeção do ventrículo esquerdo <= 40% e classe funcional II/III (NYHA). Os pacientes foram randomizados em 4 grupos: 1) controle (não treinado, n=10), 2) treinamento respiratório (n=11), 3) treinamento aeróbico (n=9) e 4) treinamento combinado (respiratório + aeróbico, n=9). A ANSM foi avaliada pela técnica de microneurografia e o FSM pela técnica de pletismografia de oclusão venosa. O controle quimiorreflexo periférico foi avaliado pela inalação de mistura gasosa hipóxica (10% de O2 e 90% N2) e o controle quimiorreflexo central pela inalação de mistura gasosa hipercapnica (7% CO2 e 93% O2). A capacidade funcional foi avaliada pelo teste cardiopulmonar. A força muscular respiratória foi avaliada pela pressão inspiratória máxima (PI Máx) e pelas pressões esofágica, gástrica e transdiafragmática. A qualidade de vida foi avaliada pelo questionário de Minessota. O treinamento aeróbico de moderada intensidade teve duração de 40 minutos, 3 vezes por semana, durante 4 meses. O treinamento respiratório consistiu em treinamento muscular inspiratório com carga de 60% da PI Máx, 30 minutos por dia, 5 dias por semana durante 4 meses. Resultados: Os treinos respiratório, aeróbico e combinado diminuíram a ANSM e aumentaram o FSM em repouso. A comparação entre os grupos não mostrou diferenças de respostas entre os grupos treinados. Os treinamentos aeróbico e combinado aumentaram a capacidade funcional (VO2 pico e carga pico). A PI Máx foi maior nos pacientes submetidos ao treinamento respiratório e combinado. A qualidade de vida melhorou nos 3 grupos treinados. O treino aeróbico e o treino respiratório reduziram a resposta de ANSM durante a estimulação dos quimiorreceptores periféricos. Não foram observadas alterações no grupo controle. Conclusão: Ambos, o treinamento respiratório e o treinamento aeróbico, melhoram o controle neurovascular em repouso. Contudo, o treinamento respiratório combinado ao treinamento aeróbico não causa benefício adicional no controle neurovascular, em pacientes com IC. O treinamento respiratório e o treinamento respiratório melhoram a resposta de ANSM à estimulação dos quimiorreceptores periféricos / Introduction: Sympathetic hyperactivity is a hallmark of heart failure (HF). Studies indicate that changes in chemoreflex sensitivity as a potential mechanism for this autonomic alteration. On the other hand, it is known that aerobic training and respiratory muscle training reduce muscular sympathetic nerve activity (MSNA). Objective: In this study we tested the following hypotheses: 1) combined respiratory training and aerobic training promove a more pronuciate effect on MSNA, muscle blood flow (MBF) and respiratory muscle strength in HF patients; 2) respiratory training and aerobic training improve chemorreflex control of MSNA. Methods: Patients aged 30 to 70 years, left ventricular ejection fraction <= 40% and functional class II / III (NYHA) were included. Patients were randomized into 4 groups: 1) control (Untrained, n = 10), 2) respiratory training (n = 11), 3) aerobic training (n = 9) and 4) combined training (n= 9). The MSNA was evaluated by the microneurography technique and the MBF by the venous occlusion plethysmography technique. Peripheral chemoreflex control was evaluated by inhaling hypoxic gas mixture (10% O2 and 90% N2) and the central chemoreflex control by inhaling the hypercapnic gas mixture (7% CO2 and 93% O2). The functional capacity was evaluated by the cardiopulmonary test. Respiratory muscle strength was assessed by maximal inspiratory pressure (PI Max) and by esophageal, gastric and transdiaphragmatic pressure. Quality of life was assessed by the Minnesota Questionnaire. Aerobic training was conducted for four months, 3 times per week, for 40 min at moderate intensity. Respiratory training consisted of inspiratory muscle training for four months, 5 times per week for 30 min, at 60% of PI Max. Results: Respiratory, aerobic and combined training reduced the MSNA and increased the MBF at rest. The comparison between the groups did not show differences of responses among the trained groups. Aerobic and combined training increased functional capacity (peak VO2 and peak load). PI Max was higher in patients submitted to combined and respiratory training. Quality of life improved in the 3 trained groups. Aerobic training and respiratory training reduced the MSNA response during stimulation of peripheral chemoreceptors. No changes were observed in the control group. Conclusion: Both respiratory training and aerobic training improve neurovascular control at rest. However, respiratory training combined with aerobic training does not cause additional benefit in neurovascular control in patients with systolic HF. Respiratory training and respiratory training improve the MSNA response to stimulation of peripheral chemoreceptors