Vítor Scotta Hentschke

Respiratory muscle training improves hemodynamics, autonomic function, baroreceptor sensitivity, and respiratory mechanics in rats with heart failure

Respiratory muscle training (RMT) improves functional capacity in chronic heart-failure (HF) patients, but the basis for this improvement remains unclear. We evaluate the effects of RMT on the hemodynamic and autonomic function, arterial baroreflex sensitivity (BRS), and respiratory mechanics in rats with HF. Rats were assigned to one of four groups: sedentary sham (n = 8), trained sham (n = 8), sedentary HF (n = 8), or trained HF (n = 8). Trained animals underwent a RMT protocol (30 min/day, 5 day/wk, 6 wk of breathing through a resistor), whereas sedentary animals did not. In HF rats, RMT had significant effects on several parameters. It reduced left ventricular (LV) end-diastolic pressure (P < 0.01), increased LV systolic pressure (P < 0.01), and reduced right ventricular hypertrophy (P < 0.01) and pulmonary (P < 0.001) and hepatic (P < 0.001) congestion. It also decreased resting heart rate (HR; P < 0.05), indicating a decrease in the sympathetic and an increase in the vagal modulation of HR. There was also an increase in baroreflex gain (P < 0.05). The respiratory system resistance was reduced (P < 0.001), which was associated with the reduction in tissue resistance after RMT (P < 0.01). The respiratory system and tissue elastance (Est) were also reduced by RMT (P < 0.01 and P < 0.05, respectively). Additionally, the quasistatic Est was reduced after RMT (P < 0.01). These findings show that a 6-wk RMT protocol in HF rats promotes an improvement in hemodynamic function, sympathetic and vagal heart modulation, arterial BRS, and respiratory mechanics, all of which are benefits associated with improvements in cardiopulmonary interaction.

Chronic electroacupuncture of the ST36 point improves baroreflex function and haemodynamic parameters in heart failure rats

Electroacupuncture (EA) has been used to treat many diseases, including heart failure (HF). This study aimed to evaluate the effects of chronic stimulation in the ST36 acupuncture point on haemodynamic parameters and baroreflex function in rats with HF. Cardiovascular parameters assessed were heart rate (HR), blood pressure (BP), and the reflex cardiovascular response of HR triggered by stimulation of baroreceptors in animals with HF subsequent to acute myocardial infarction (AMI). Male Wistar rats were divided into three groups: Sham Control - animals without HF and without EA; HF Control group - animals with HF and without EA; and HF EA group - animals with HF that received the EA protocol. Six weeks after surgical induction of AMI, the EA protocol (8 weeks, 5 times a week) was performed. The protocol was applied with EA at the ST36 point, frequency of 2 Hz, pulse of 0.3 ms and intensity of 1-3 mA for 30 min. Haemodynamic parameters and baroreceptor function were assessed. There was no difference between groups in the variables HR, systolic blood pressure (SBP) and diastolic blood pressure (DBP), which were evaluated with awake animals (p>0.05). There was an increase in the mean arterial pressure (MAP) in the HF EA group compared to the HF Control group (p<0.05). The maximum gain of the baroreflex heart rate response (Gain) was higher in the HF EA group than the HF Control and Sham Control groups. Chronic EA in the ST36 point increased the MAP and baroreflex sensitivity in rats with HF.

Ultrasound Modulates Skeletal Muscle Cytokine Levels in Rats with Heart Failure

Heart failure is a multisystemic disorder that leads to an imbalance between pro- and anti-inflammatory cytokines. Therapeutic ultrasound (TU) has been reported to modulate the inflammatory process. The aim of this study was to evaluate the effect of TU on pro- and anti-inflammatory cytokine levels in soleus muscle and plasma of rats with heart failure. Thirty male Wistar rats (230-260 g) were submitted to ligation of the left coronary artery or sham surgery. Six weeks after surgery, TU was administered directly to the right lower limb. The results indicate that TU promotes reduction of pro-inflammatory cytokine levels (tumor necrosis factor α, interleukin-6) and increases anti-inflammatory cytokine levels (interleukin-10) in the soleus muscle of rats with heart failure. This is the first study to find that TU can modulate cytokine levels in rats with heart failure. Additionally, this is a first report that TU can modulate interleukin-10 levels in the soleus muscle.

Functional capacity in a rat model of heart failure: impact of myocardial infarct size

What is the central question of this study? To the best of our knowledge, no studies have evaluated oxygen uptake, carbon dioxide production and exercise tolerance in rats that have undergone myocardial infarction classified by myocardial infarct (MI) size. What is the main finding and its importance? Oxygen uptake and exercise intolerance are MI size dependent, and classification based on MI size can distinguish rats with functional capacity impairment. Rats with a large MI (>40% of the left ventricle) might provide a good model for the testing of new therapies that have the potential to modify the variables of functional capacity.

Respiratory muscle training decreases diaphragm DNA damage in rats with heart failure

Respiratory muscle training (RMT) promotes beneficial effects on respiratory mechanics, heart and lung morphological changes, and hemodynamic variables in rats with heart failure (HF). However, the relation between RMT effects and diaphragm oxidative stress remains unclear. Therefore, the aim of this study was to evaluate the RMT effects on diaphragm DNA damage in HF rats. Wistar rats were allocated into 4 groups: sedentary sham (Sed-Sham, n = 8), trained sham (RMT-Sham, n = 8), sedentary HF (Sed-HF, n = 8), and trained HF (RMT-HF, n = 8). The animals underwent a RMT protocol (30 min/day, 5 days/week for 6 weeks), whereas sedentary animals did not exercise. Groups were compared by a two-way ANOVA and Tukeys post hoc tests. In rats with HF, RMT promoted reduction in pulmonary congestion (p < 0.0001) and left ventricular end diastolic pressure (p < 0.0001). Moreover, RMT produced a decrease in the diaphragm DNA damage in HF rats. This was demonstrated through the reduction in the percentage of tail DNA (p < 0.0001), tail moment (p < 0.01), and Olive tail moment (p < 0.001). These findings showed that a 6-week RMT protocol in rats with HF promoted an improvement in hemodynamic function and reduces diaphragm DNA damage.

A novel approach to the application of electroacupuncture in awake rats

The primary focus of many animal studies of electroacupuncture (EA) is on the overall effects of the treatment, without due consideration of the impact of how the needles are applied in animal models. Most experimental studies of EA use anaesthesia before needle insertion and electrical stimulation, or alternatively use restraining devices while the animals remain awake, either of which may confound the effects of the needling per se. In a recent study, Wang et al 1 reported that rats remained in a polyethylene cylinder during the application of EA, without the need for either restraints or anaesthesia. Based on this observation, and given the potential difficulties that may be encountered during the application of EA, we set out to create a novel bottle-based device to help facilitate administration of EA without the use of anaesthesia or restraints. A customised bottle device was fashioned out of a wooden board and six 500 mL polyethylene terephthalate (PET) water bottles. The necks of the bottles were cut off, fixed to the wooden surface, and used as burrows (figure 1). The cut edge of each bottleneck was covered with electrical tape to avoid any injury. Using this device it was possible to stimulate up to six conscious animals simultaneously without anaesthesia or restraints, thus …