ANÁLISE DOS RECEPTORES DE ACETILCOLINA (nAChRs) NA MUSCULATURA ESQUELÉTICA DE RATOS COM INSUFICIÊNCIA CARDÍACA SUBMETIDOS AO TREINAMENTO AERÓBICO

Heart failure (HF) is a syndrome initiated by a reduction in cardiac function and characterized by the activation of compensatory mechanisms and muscle myopathy. Fatigue and dyspnea are the most common symptoms of this disease, associated with the reduction of the oxidative capacity, changes in the fibers type I to type II, alterations in the expression of myogenic regulatory factors (MRFs) and in the neuromuscular junction (NMJs). Aerobic training is considered a widely accepted practice to minimize the consequences of the symptoms caused by HF, improving the life quality and can reverse abnormalities of cardiac and skeletal muscle, and modulate the NMJ. The diaphragm is the most important inspiratory muscle in mammals and is one of the most affected in HF; aerobic training changes the electrophysiological properties of the diaphragm during fatigue and promotes muscle endurance. Thus, the hypothesis of this study is that the changes that occur in HF are associated with alterations in the NMJs, in the expression of nAChRs and aerobic training can attenuate these changes. The aim of this study was to evaluate the distribution and the expression of nAChRs subunits in rats with HF submitted to an aerobic training. We used 44 male wistar rats (90 to 100g), divided into four groups: Control (C), Aerobic Training (TR), Aortic Stenosis (AS) and Aortic Stenosis with Aerobic Training (ASTR). Aortic stenosis was induced by the insertion of a silver clip of 0.6 mm in diameter in the ascending aorta. After 18 weeks of surgery, the animals with AS were evaluated by echocardiography for evaluating LV hypertrophy. The others were randomly divided into C, TR and ASTR groups. The animals of TR and ASTR groups were submitted to aerobic training on a treadmill for 10 weeks (5 days/ week). The diaphragm muscle was used to assess the expression of the nAChRs subunits (γ, α, e, δ and β1) and MRFs (Myogenin and MyoD) by RT-qPCR and Western blot. We also analyzed the distribution of nAChRs and terminal axon along the muscle fiber with immunostaining using α-bungarotoxin associated with rhodamine and anti-neurofilament, respectively. After the immunostaining, the analysis was performed using laser scanning confocal microscope and the area of nAChRs was measured using the Image J software. Our results showed an increase in the mRNA of γ subunits, α, e, δ and β1 in the AS group and decreased expression of γ α, β1 and δ in the ASTR group. Only the e subunit expression in the group ASTR was more expressed. The expression of the MRFs, Myogenin and MyoD did not change in the groups studied. The immunostaining of nAChRs revealed that there was no difference in the morphology of the receptors that show a distribution as a continuous branches or pretzel. The area analysis revealed a modulation in the distribution of nAChRs,being high in AS(20 at 30 μm 2 ) and ASTR(31 at 40 μm 2 ) groups. Our study showed changes in the distribution and expression of nAChRs subunits during heart failure. Aerobic training was beneficial and attenuated nAChRs subunits changes in the neuromuscular junctions. This protocol could be critical to the intervention of future therapies for life quality improvement in patients with heart failure.