Role of aerobic physical training on cardiac autonomic and morphophysiological dysfunction in hypertensive rats subjected to ovarian hormone deprivation

Here we investigated the effects of physical training on cardiovascular autonomic control and cardiac morphofunctional parameters in spontaneously hypertensive rats (SHRs) subjected to ovarian hormone deprivation. Forty-eight 10-week-old SHRs were divided into two groups: ovariectomized (OVX, n=24) and sham (SHAM, n=24). Half of each group (n=12) was trained by swimming for 12 weeks (OVX-T and SHAM-T). Cardiac morphology and functionality were assessed using echocardiography, and autonomic parameters were assessed using double pharmacological autonomic block, baroreflex sensitivity (BRS), and analyses of heart rate variability (HRV) and blood pressure variability (BPV). Ovariectomy did not influence the cardiac autonomic tonus balance unlike physical training, which favored greater participation of the vagal autonomic tonus. Ovariectomy and aerobic physical training did not modify HRV and BRS, unlike BPV, for which both methods reduced low-frequency oscillations, suggesting a reduction in sympathetic vascular modulation. Untrained ovariectomized animals showed a reduced relative wall thickness (RWT) and increased diastolic and systolic volumes and left ventricular diameters, resulting in increased stroke volume. Trained ovariectomized animals presented reduced posterior wall thickness and RWT as well as increased final diastolic diameter, left ventricular mass, and stroke volume. Ovarian hormone deprivation in SHRs promoted morphofunctional adaptations but did not alter the evaluation of cardiac autonomic parameters. In turn, aerobic physical training contributed to a more favorable cardiac autonomic balance to the vagal autonomic component and promoted morphological adaptations but had little effect on cardiac functionality.

Effects of respiratory muscle training on parasympathetic activity in diabetes mellitus

This study verified the effects of respiratory muscle training (RMT) on hemodynamics, heart rate (HR) variability, and muscle morphology in rats with streptozotocin-induced diabetes mellitus (DM). Thirty-six male Wistar rats were randomized into 4 groups and 34 completed the study: i) sham-sedentary (Sham-ST; n=9); ii) sham-RMT (Sham-RMT; n=9); iii) DM-sedentary (DM-ST; n=8); and iv) DM-RMT (DM-RMT; n=8). Hemodynamics were assessed by central cannulation, and R-R intervals were measured by electrocardiogram. In addition, the effects of RMT on the cross-sectional area of the diaphragm, anterior tibial, and soleus muscles were analyzed. The induction of DM by streptozotocin resulted in weight loss, hyperglycemia, reduced blood pressure, and attenuated left ventricular contraction and relaxation (P<0.05). We also observed a decrease in root mean square of successive differences between adjacent RR intervals (RMSSD) index and in the cross-sectional area of the muscles assessed, specifically the diaphragm, soleus, and anterior tibial muscles in diabetic rats (P<0.05). Interestingly, RMT led to an increase in RMSSD in rats with DM (P<0.05). The induction of DM produced profound deleterious changes in the diaphragmatic and peripheral muscles, as well as impairments in cardiovascular hemodynamics and autonomic control. Nevertheless, RMT may beneficially attenuate autonomic changes and improve parasympathetic modulation.

Heart rate and cardiac autonomic responses to concomitant deep breathing, hand grip exercise, and circulatory occlusion in healthy young adult men and women

BACKGROUND: Deep breathing (DB) and handgrip (HG) exercise -with and without circulatory occlusion (OC) in muscle-, have been shown to have beneficial effects on cardiovascular function; however, the combination of these maneuvers on heart rate (HR) and cardiac sympathovagal balance have not been previously investigated. Therefore, the aim of the present study was to evaluate the effect of simultaneous DB, HG, and OC maneuvers on the sympathovagal balance in healthy women and men subjects. METHODS AND RESULTS: Electrocardiogram and ventilation were measured in 20 healthy subjects (Women: n = 10; age = 27 ± 4 years; weight = 67.1 ± 8.4 kg; and height = 1.6 ± 0.1 m. Men: n = 10; age = 27 ± 3 years; weight = 77.5 ± 10.1 kg; and height = 1.7 ± 0.1 m) at baseline and during DB, DB + HG, or DB + HG + OC protocols. Heart rate (HR) and respiratory rate were continuously recorded, and spectral analysis of heart rate variability (HRV) were calculated to indirectly estimate cardiac autonomic function. Men and women showed similar HR responses to DB, DB + HG and DB + HG + OC. Men exhibited a significant HR decrease following DB + HG + OC protocol which was accompanied by an improvement in cardiac autonomic control evidenced by spectral changes in HRV towards parasympathetic predominance (HRV High frequency: 83.95 ± 1.45 vs. 81.87 ± 1.50 n.u., DB + HG + OC vs. base-line; p < 0.05). In women, there was a marked decrease in HR after completion of both DB + HG and DB + HG + OC tests which was accompanied by a significant increase in cardiac vagal tone (HRV High frequency: 85.29 ± 1.19 vs. 77.93 ± 0.92 n.u., DB + HG vs. baseline; p < 0.05). No adverse effects or discomfort were reported by men or women during experimental procedures. Independent of sex, combination of DB, HG, and OC was tolerable and resulted in decreases in resting HR and elevations in cardiac parasympathetic tone. CONCLUSIONS: These data indicate that combined DB, HG and OC are effective in altering cardiac sympathovagal balance and reducing resting HR in healthy men and women.

Are there relationship between internal and external load of aerobic training with heart rate variability in women? / Há relação da carga interna e externa do treinamento aeróbio com variabilidade da frequência cardíaca em mulheres?

ABSTRACT The purpose was to investigate the relationship between internal training load (ITL), external training load (ETL) and heart rate variability (HRV) in women. 16 women (48.2 ± 6.4 yrs) performed HRV recordings (i.e. lnRMSSD - cardiovagal modulation) and Incremental Shuttle Walk Test (ISWT) before and after 12 aerobic training sessions. HRV threshold (HRVT) were used to prescribe aerobic ETL. The session rating of perceived exertion (s-RPE) was analyzed and served as the measure of ITL. The score found for ITL in the 12 sessions was 2878 ± 380 arbitrary units and ETL were 36822 ± 5852 m. A significant difference was observed in the lnRMSSD (3.14 ± 0.30 vs. 3.43 ± 0.38 ms−1; P = 0.001). There were observed large correlation between lnRMSSD at baseline vs ISWT (r = 0.73, P = 0.001), HRVT (r = 0.67, P = 0.004) and ITL (r = 0.62, P = 0.011). Very large correlation between individual smallest worthwhile change lnRMSSD after training and ITL (r = 0.81, P = 0.0001) was observed. There is a strong association between the HRV and aerobic performance (HRVT and ISWTdistance) and strong relationship between HRV and the potential to accumulate ITL, but not aerobic ETL in women.

RESUMO O objetivo foi investigar a relação da carga interna de treinamento (CIT), carga externa de treinamento (CET) e variabilidade da frequência cardíaca (VFC) em mulheres. 16 mulheres (48,2 ± 6,4 anos) realizaram medidas de VFC em repouso (variável lnRMSSD - modulação cardiovagal) e o teste incremental de caminhada (TIC) antes e depois de 12 semanas de treinamento aeróbio. O limiar da VFC (LVFC) foi utilizado para prescrição da CET. A percepção subjetiva de esforço (PSE) foi utilizada para cálculo da CIT. O valor de CIT encontrado nas 12 sessões foi de 2878 ± 380 unidades arbitrárias e para CET de 36822 ± 5852 m. Foi observada diferença significativa para lnRMSSD (3,14 ± 0,30 vs. 3,43 ± 0,38 ms−1; P = 0.001). Verificou-se uma correlação grande entre lnRMSSD basal e TIC (r = 0.73, P = 0.001), LVFC (r = 0.67, P = 0.004) e CIT (r = 0.62, P = 0.011). Foi encontrada uma correlação muito grande entre a mínima diferença detectável individual do lnRMSSD após treinamento e CIT. Conclui-se que há uma forte relação entre VFC e performance aeróbia (LVFC e TICdistância), VFC e acúmulo de CIT, porém, sem relação com a CET acumulada nas 12 semanas nas mulheres estudadas.

Neuroanatomical Circuitry between Kidney and Rostral Elements of Brain: a Virally Mediated Transsynaptic Tracing Study in Mice / 华中科技大学学报（医学）（英德文版）

The identity of higher-order neurons and circuits playing an associative role to control renal function is notwell understood.We identified specific neural populations of rostral elements of brain regions that project multisynaptically to the kidneys in 3~ days after injecting a retrograde tracer pseudorabies virus (PRV)-614 into kidney of 13 adult male C57BL/6J strain mice.PRV-614 infected neurons were detected in a number of mesencephalic (e.g.central amygdala nucleus),telencephalic regions and motor cortex.These divisions included the preoptic area (POA),dorsomedial hypothalamus (DMH),lateral hypothalamus,arcuate nucleus (Arc),suprachiasmatic nucleus (SCN),periventricular hypothalamus (PeH),and rostral and caudal subdivision of the paraventricular nucleus of the hypothalamus (PVN).PRV-614/Tyrosine hydroxylase (TH) double-labeled cells were found within DMH,Arc,SCN,PeH,PVN,the anterodorsal and medial POA.A subset of neurons in PVN that participated in regulating sympathetic outflow to kidney was catecholaminergic or serotonergic.PRV-614 infected neurons within the PVN also contained arginine vasopressin or oxytocin.These data demonstrate the rostral elements of brain innervate the kidney by the neuroanatomical circuitry.

Análise da variabilidade da frequência cardíaca em cordeiros da raça Bergamácia, do nascimento aos 35 dias de idade / Analysis of heart rate variability in Bergamasca newborn lambs from birth at 35th days of age

A atividade do sistema nervoso autônomo sobre o coração pode ser verificada pela variabilidade da frequência cardíaca (VFC), método que quantifica e assim infere sobre a modulação autonômica cardíaca, refletindo o funcionamento do sistema nervoso autônomo. Durante o período neonatal, diferenças significativas no que se refere à maturação autonômica são descritas em diversas espécies. Embora a espécie ovina venha sendo utilizada como modelo experimental em diversos protocolos em neonatologia e cardiologia em humanos, estudos descritivos sobre a VFC utilizando animais saudáveis e não sedados são escassos na literatura. O objetivo do estudo foi descrever a VFC em cordeiros da raça Bergamácia durante os primeiros 35 dias de idade. Foram realizados exames eletrocardiográficos em 20 cordeiros da raça Bergamácia a partir do nascimento e semanalmente até o 35° dia de idade. A VFC foi analisada pelo intervalo RR normal (batimentos sinusais), pela frequência cardíaca, pelo índice de tônus vasovagal (iTVV), pela raiz quadrada da média do quadrado das diferenças entre intervalos RR normais adjacentes (RMSSD) e pela raiz quadrada da somatória do quadrado das diferenças dos valores individuais em relação ao valor médio, dividido pelo número de iR-R em 90 segundos - VFC global (RMSM). Todos os parâmetros se alteraram ao longo das semanas. A frequência cardíaca média elevou-se entre o nascimento e os primeiros sete dias de idade, com decréscimo nas quatro semanas subsequentes, sendo o menor valor encontrado aos 35 dias de idade (145,63±37,80bpm). Entre 21, 28 e 35 dias de idade, o iTVV elevou-se significativamente, o RMSM a partir do 28º dia, e, aos 35 dias, o RMSSD, reflexo da ativação parassimpática, exibiu diferenças em relação aos momentos subsequentes. O início da predominância parassimpática, refletida nos índices da VFC, particularmente o iTVV, ocorre aos 21 dias de idade. A partir dos 35 dias de idade, os índices RMSM e RMSSD podem ser utilizados como marcadores fidedignos das mudanças nos efeitos simpático e parassimpático sobre o coração de cordeiros.(AU)

Autonomic nervous system activity can be checked by heart rate variability (HRV), method that quantifies and thus infers on cardiac autonomic modulation, reflecting the functioning of the autonomic nervous system. During the neonatal period significant differences as regards the autonomic maturation, are described in various species. Although the sheep come being used as experimental model of several protocols in neonatology and cardiology in humans, descriptive studies about the VFC using healthy animals and not sedated are scarce in the literature. The objective of this study was to describe the HRV in the Bergamasca race lambs during the first 35 days of age. Electrocardiographic examinations were performed in 20 lambs of the Bergamasca race from birth, in the7th, 14th, 21st, 28th, and 35th days of age. The HRV was analyzed by normal RR interval (sinus rate), heart rate, index of vagal tone, and the cardiovascular manifestations (square root of the average of the square of the differences between normal RR intervals adjacent). All parameters have changed over the weeks. The average heart rate increased between the birth and the first seven days of age, with decrease in the subsequent four weeks, being the smallest value found at 35 days of age (145.63±37.80bpm). Between 21, 28 and 35 days of age, the iTVV increased significantly, the RMSM from the 28 day, and 35 days, the cardiovascular manifestations, reflex parasympathetic activation, exhibited differences in relation to subsequent times. The beginning of parasympathetic dominance, reflected in the HRV indices, particularly the iTVV, occurs at 21 days of age. From the 35 days of age, the RMSM indices and RMSSD can be used as reliable markers of change in sympathetic and parasympathetic effect on the heart of lambs.(AU)

Comparação da resposta autonômica cardiovascular de praticantes de musculação, corredores de longa distância e não praticantes de exercício / Comparison of cardiovascular autonomic response among body builders, long distance runners and non-trained

Objetivou-se comparar a resposta autonômica cardiovascular (RAC) de praticantes de musculação, corredores de longa distância e não praticantes de exercício. Homens, 21 a 55 anos, foram agrupados em: Praticantes Musculação (PM, n = 31); Praticantes Corrida (PC, n = 28); Controle (C, n = 35). Foram selecionadas quatro técnicas para avaliação da RAC: Frequência cardíaca de repouso (FCR), Teste pressórico do frio (TPF), Variabilidade da FC (VFC) e recuperação da FC pós-teste máximo em esteira. A FCR foi menor no grupo PC (PC = 54 ± 2; PM= 62 ± 2; C = 65 ± 2 bpm; média ± EPM). A recuperação da FC aos 60 s pós-teste de esforço foi maior no grupo PC (PC = 34 ± 3; PM = 23 ± 1; C = 24 ± 2; bpm). Quanto aos parâmetros espectrais de alta (HF) e baixa (LF) frequência da VFC, o grupo PC apresentou maior HF (55,1 ± 4,0 n.u) e menor LF (43,1 ± 4,0 n.u) comparado ao grupo C (HF = 40,7 ± 3,3; LF = 56,7 ± 3,5 n.u). O grupo PM não apresentou qualquer diferença de RAC em comparação ao grupo C. Conclui-se que prática contínua em musculação por longo prazo, diferentemente da prática de corrida de longa distância, não é capaz de alterar significativamente a RAC.

The aim of the study was to compare the cardiovascular autonomic response (CAR) of recreational weight trainers, long distance runners and non-exercised subjects. Men, 21 to 55 years old, were grouped in: recreational weight trainers (W, n = 31), long distance runners (R, n = 28) and non-exercised (C, n = 35). Four strategies of evaluation of the CAR were selected: Resting heart rate (RHR), cold pressor test (CPT), heart rate variability (HRV) and heart rate recovery (HHR) following maximal exercise test. The RHR was lower (R = 54 ± 2; W = 62 ± 2; C= 65 ± 2 bpm; mean ± SE) and the HHR 60s post exercise was larger in the R group (R = 34 ± 3; W = 23 ± 1; C = 24 ± 2 bpm). The R group presented larger high-frequency (HF; 55.1 ± 4.0 n.u) and smaller low-frequency (LF; 43.1 ± 4.0 n.u) components of HRV than C group (HF = 40.7 ± 3.3; LF = 56.7 ± 3.5 n.u.). The W group did not show any differences compared to C group. The study's conclusion was that long-term weight-training program, unlike of long-term running training, it is not able to alter significantly the regulatory pattern of CAR.

Insights into the clinical and functional significance of cardiac autonomic dysfunction in Chagas disease / Considerações sobre o significado clínico-funcional da disfunção autonômica cardíaca na doença de Chagas

INTRODUCTION: Exclusive or associated lesions in various structures of the autonomic nervous system occur in the chronic forms of Chagas disease. In the indeterminate form, the lesions are absent or mild, whereas in the exclusive or combined heart and digestive disease forms, they are often more pronounced. Depending on their severity these lesions can result mainly in cardiac parasympathetic dysfunction but also in sympathetic dysfunction of variable degrees. Despite the key autonomic effect on cardiovascular functioning, the pathophysiological and clinical significance of the cardiac autonomic dysfunction in Chagas disease remains unknown. METHODS: Review of data on the cardiac autonomic dysfunction in Chagas disease and their potential consequences, and considerations supporting the possible relationship between this disturbance and general or cardiovascular clinical and functional adverse outcomes. RESULTS: We hypothesise that possible consequences that cardiac dysautonomia might variably occasion or predispose in Chagas disease include: transient or sustained arrhythmias, sudden cardiac death, adverse overall and cardiovascular prognosis with enhanced morbidity and mortality, an inability of the cardiovascular system to adjust to functional demands and/or respond to internal or external stimuli by adjusting heart rate and other hemodynamic variables, and immunomodulatory and cognitive disturbances. CONCLUSIONS: Impaired cardiac autonomic modulation in Chagas disease might not be a mere epiphenomenon without significance. Indirect evidences point for a likely important role of this alteration as a primary predisposing or triggering cause or mediator favouring the development of subtle or evident secondary cardiovascular functional disturbances and clinical consequences, and influencing adverse outcomes.

INTRODUÇÃO: Lesões isoladas ou combinadas de várias estruturas do sistema nervoso autônomo ocorrem nas formas crônicas da doença de Chagas. Na forma indeterminada, as lesões são discretas e podem estar até ausentes, enquanto nas formas cardíaca e digestória exclusivas ou combinadas elas são comumente mais pronunciadas. Na dependência da sua maior ou menor severidade, estas lesões podem resultar em variáveis graus de disfunção parassimpática e/ou simpática, principalmente a primeira. Apesar da crítica influência autonômica sobre o funcionamento cardiovascular, o significado fisiopatológico e clínico, notadamente em longo prazo, da disfunção autonômica cardíaca permanece desconhecido na doença de Chagas. MÉTODOS: Revisão sobre a disfunção autonômica cardíaca na doença de Chagas e suas potenciais consequências, como base para considerações acerca da possível relação entre este distúrbio e desfechos clínicos e funcionais globais e cardiovasculares desfavoráveis. RESULTADOS: Os potenciais desfechos que a disautonomia cardíaca pode variavelmente determinar ou predispor na doença de Chagas incluem: arritmias transitórias ou sustentadas, morte súbita, mal prognóstico global e cardiovascular, morbi-mortalidade aumentada, deficiente adaptação cardiovascular a demandas funcionais e/ou em resposta a estímulos internos e externos por meio de ajustes da frequência cardíaca e outras variáveis hemodinâmicas, e distúrbios imunomoduladores e psico-funcionais. CONCLUSÕES: A alteração da modulação autonômica cardíaca na doença de Chagas pode não representar mero epifenômeno sem significado. Evidências indiretas sugerem papel importante desta alteração como fator predisponente ou determinante primário para o desenvolvimento secundário de distúrbios funcionais manifestos ou não e consequências clínicas cardiovasculares, e para a ocorrência de desfechos desfavoráveis.

História familiar positiva de diabetes altera a resposta cronotrópica ao exercício agudo / Positive diabetes family history alters chronotropic response to acute exercise

O objetivo do presente estudo foi verificar os efeitos de uma sessão de exercício aeróbio (SEA) no perfil metabólico e hemodinâmico em filhos de diabéticos do tipo II. Jovens saudáveis do sexo masculino foram divididos em dois grupos: filhos de diabéticos (FD, n = 7) e filhos de normoglicêmicos (FN, n = 7). Foram realizadas medidas metabólicas (triglicérides e glicemia) e cardiovasculares (pressão arterial, PA, e frequência cardíaca, FC) em repouso, durante e após a SEA. A SEA foi realizada em esteira ergométrica com duração de 30 minutos e intensidade progressiva. Os grupos apresentaram valores semelhantes em relação ao triglicérides, PA e FC em repouso. A glicemia de jejum do grupo FD foi maior em relação ao grupo FN (99 ± 2 versus 89 ± 2mg/dL). O grupo FD apresentou maior resposta cronotrópica no início da SEA quando comparado ao grupo FN (86 ± 4 versus 125 ± 8bpm), mas a FC foi semelhante entre os grupos nas demais intensidades. No quinto minuto de recuperação da SEA a FC foi maior no grupo FD comparado ao grupo FN (FN: 88 ± 3 versus FD: 97 ± 4bpm). A PA foi semelhante entre os grupos durante e após a SEA. Os resultados demonstram que filhos de diabéticos jovens já apresentam alterações metabólicas em repouso e resposta exacerbada da FC no início e nos primeiros minutos de recuperação da SEA, sugerindo um maior risco cardiovascular nessa população.

The aim of this study was to verify the effects of one aerobic exercise session (AES) on the metabolic and hemodynamic profile in diabetes type II offspring. Healthy young males were assigned into 2 groups: diabetic offspring (DO, n=7) and euglicemic offspring (EO, n=7). Metabolic (triglycerides and glucose levels) and cardiovascular (arterial pressure, AP, heart rate, HR) measures were realized before, during and after the AES. The AES was realized on a treadmill during 30 minutes, with progressive intensity. The groups showed similar triglycerides, AP and HR values at rest. The glucose level was higher in DO group when compared to the ED group (99±2 vs. 89±2 mg/dL). The DO group showed higher chronotropic response at the beginning of AES when compared to the EO group (86±4 vs. 125±8 bpm), however, the HR was similar between the groups at the other exercise intensities. At the fifth minute of the recovery, the HR was higher in the DO group when compared to the EO group (FN: 88 ± 3 vs FD: 97± 4 bpm). The AP was similar between groups during and after the AES. The results showed that young diabetic offspring presented metabolic alterations at rest, and exacerbated HR response at the beginning and in the recovery period of the AES, suggesting a higher cardiovascular risk in this population.

Controle autonômico da frequência cardíaca de pacientes com doenças cardiorrespiratórias crônicas e indivíduos saudáveis em repouso e durante a manobra de acentuação da arritmia sinusal respiratória / Autonomic control of heart rate in patients with chronic cardiorespiratory disease and in healthy participants at rest and during a respiratory sinus arrhythmia maneuver

OBJETIVO: Avaliar a modulação autonômica da frequência cardíaca (FC) em repouso, na postura supina e durante a manobra de acentuação da arritmia sinusal respiratória (M-ASR) de pacientes com doença pulmonar obstrutiva crônica (DPOC) ou com insuficiência cardíaca crônica (ICC). MÉTODOS: Vinte e oito homens foram subdivididos em três grupos: 10 com DPOC (GD) e 69±9 anos; 9 com ICC (GI) e 62±8 anos; e 9 saudáveis (GC) com 64±5 anos. Em repouso, os intervalos R-R a partir do sinal eletrocardiográfico foram obtidos nas seguintes situações: 1) 15 minutos na posição supina e 2) 4 minutos durante M-ASR na posição supina. Os dados foram analisados nos domínios do tempo (índices RMSSD e SDNN) e da frequência. Durante M-ASR, foram calculadas a razão expiração/inspiração (E/I) e a diferença inspiração/expiração (∆IE). RESULTADOS: Os principais achados mostraram que os pacientes com ICC apresentaram menores valores de RMSSD (12,2±2,6 vs 20,4±6,5), BFab (99,2±72,7 vs 305,3±208,9) e AFun (53,4±29,9 vs 178,9±113,1) quando comparados ao controle. Além disso, a banda de BFab foi significantemente reduzida no grupo DPOC quando comparado ao controle (133,8±145,5 vs 305,3±208,9). Adicionalmente, pacientes com ICC e DPOC mostraram menor razão E/I (1,1±0,06 vs 1,2±0,1 e 1,1±0,03 vs 1,2±0,1) e ∆IE (7,0±3,5 vs 12,7±0,1 e 4,9±1,6 vs 12,7±0,1), respectivamente, comparados ao GC durante a M-ASR. CONCLUSÃO: Os resultados deste estudo sugerem que tanto a DPOC como a ICC produzem impacto negativo sobre o controle autonômico da FC.

OBJECTIVE: To evaluate the autonomic modulation of heart rate (HR) at rest in the supine position and during a respiratory sinus arrhythmia maneuver (M-RSA) among participants with chronic obstructive pulmonary disease (COPD) or with chronic heart failure (CHF). METHODS: Twenty-eight men were divided into three groups: ten with COPD, aged 69±9 years; nine with CHF, aged 62±8 years; and nine healthy participants aged 64±5 years (controls). At rest, the R-R interval of the electrocardiographic signal was obtained in the following situations: 1) 15 min in the supine position; and 2) 4 min during M-RSA in the supine position. The data were analyzed in the time domain (RMSSD and SDNN indices) and the frequency domain (LFab and HFab). During M-RSA, the expiratory/inspiratory ratio (E/I) and the inspiratory/expiratory difference (∆IE) were calculated. RESULTS: The main findings showed that the CHF patients presented lower RMSSD (12.2±2.6 vs. 20.4±6.5), LFab (99.2±72.7 vs. 305.3±208.9) and HFab (53.4±29.9 vs. 178.9±113.1), compared with the controls. The LFab band was significantly lower in the COPD group than in the controls (133.8±145.5 vs. 305.3±208.9). Additionally, both CHF patients and COPD patients showed lower E/I ratios (1.1±0.06 vs. 1.2±0.1 and 1.1±0.03 vs. 1.2±0.1) and ∆IE values (7.0±3.5 vs. 12.7±0.1 and 4.9±1.6 vs. 12.7±0.1), respectively, compared with the controls during M-RSA. CONCLUSION: The results from this study suggest that both COPD and CHF have a negative impact on the autonomic control of heart rate.

Resposta taquicárdica e controle autonômico no exercício físico em modelo genético de insuficiência cardíaca / Tachycardic response and autonomic control in physical exercise in genetic model of cardiac insufficiency

O aumento da atividade nervosa simpática e a taquicardia em repouso ou durante esforços físicos estão associados ao aumento da morbimortalidade, mesmo na ausência de sinais clínicos de doença cardíaca. Sabendo-se da importância dos receptores α2A/α2C-adrenérgicos na modulação da atividade nervosa e frequência cardíaca (FC), o presente trabalho utiliza um modelo genético de cardiomiopatia induzida por excesso de catecolaminas circulantes baseado na inativação gênica dos receptores α2A/α2C-adrenérgicos em camundongos (α2A/α2CKO) para verificar a resposta da FC ao exercício físico (EF), assim como o controle simpatovagal da FC ao EF. Testou-se a hipótese de que haveria resposta taquicárdica exacerbada durante o EF nos camundongos α2A/α2CKO mesmo quando a função cardíaca ainda estivesse preservada em repouso, sendo o receptor α2A-adrenérgico o principal responsável por essa resposta. Camundongos machos da linhagem C57Bl6J, controle (CO) e com inativação gênica para os receptores α2A (α2AKO), α2C α2CKO) e α2A/α2CKO foram submetidos a um teste de tolerância ao esforço físico. Outros dois grupos de camundongos, CO e α2A/α2CKO, foram submetidos ao bloqueio farmacológico dos receptores muscarínicos e β-adrenérgicos e ao EF progressivo para se avaliar a contribuição simpatovagal para a taquicardia de EF. Observou-se intolerância ao esforço físico (1.220 ± 18 e 1.460 ± 34 vs. 2.630 ± 42m, respectivamente) e maior taquicardia ao EF (765 ± 16 e 792 ± 13 vs. 603 ± 18bpm, respectivamente) nos camundongos α2AKO e α2A/α2CKO vs. CO. Além disso, o balanço autonômico estava alterado nos camundongos α2A/α2CKO pela hiperatividade simpática e menor efeito vagal cardíaco. Esses resultados demonstram a importância dos receptores α2A/α2C-adrenérgicos no controle autonômico não só no repouso, mas também durante o EF, sendo o receptor ...

Increase of sympathetic nervous activity and tachycardia at rest or during physical exertions are associated with increase of morbimortality, even in the absence of clinical signs of cardiac disease. Considering the importance of the α2A/α2C-adrenergic receptors in the modulation of the nervous activity and heart rate (HR), the present study uses a genetic model of cardiomyopathy induced by excess of circulating catecholamine in the gene inactivation of the α2A/α2 -adrenergic receptors in mice (α2A/α2CKO) to verify the HR response to physical exercise (PE), as well as the sympathetic-vagal control of the HR to PE. The hypothesis is that there would be exacerbated tachycardic response during PE in α2A/α2CKO mice even when the cardiac function was still preserved at rest, being the α2A-adrenergic receptor the main reason for this response. Male mice of the C57Bl6J lineage, control (CO) and with gene inactivation for the a2A (α2AKO), α2C α2CKO) and α2A/α2CKO receptors were submitted to tolerance to a physical exercise test. Two other groups of mice, CO and α2A/α2CKO, were submitted to pharmacological blocking of the muscarinic and β-adrenergic receptors as well as to progressive PE to assess the sympathetic-vagal contribution to PE tachycardia. Intolerance to physical exercise (1.220 ± 18 and 1.460 ± 34 vs. 2.630 ± 42m, respectively) and higher tachycardia to PE (765 ± 16 e 792 ± 13 vs. 603 ± 18 bpm, respectively) in the α2AKO and α2A/α2CKO vs. CO mice was observed. Moreover, the autonomic balance was altered in the α2A/α2CKO mice by the sympathetic hyperactivity and lower cardiac vagal effect. These outcomes demonstrated the importance of the α2A/α2C-adrenergic receptors in autonomic control not only at rest, but also during PE, being theα2A-adrenergic receptor responsible for the sympathetic hyperactivity and lower ...