Exercise training preserves vagal preganglionic neurones and restores parasympathetic tonus in heart failure

• Published in: The Journal of physiology 2016-11, Vol.594 (21), p.6241-6254
• Main Authors: Ichige, Marcelo H. A., Santos, Carla R., Jordão, Camila P., Ceroni, Alexandre, Negrão, Carlos E., Michelini, Lisete C.
• Format: Article
• Language: English
• Subjects: aerobic training; Animals; autonomic dysfunction; Autonomic Fibers, Preganglionic - physiology; Blood Pressure; Cardiovascular; Cardiovascular Conditions, Disorders and Treatments; Cardiovascular Physiology; ChAT immunoreactivity; DBH immunoreactivity; Heart - innervation; heart failure; Heart Failure - physiopathology; Heart Rate; Male; Neurons - physiology; Physical Conditioning, Animal; Rats; Rats, Wistar; Research Paper; Vagus Nerve - cytology; Vagus Nerve - physiology
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/JP272730

Key points Heart Failure (HF) is accompanied by reduced ventricular function, activation of compensatory neurohormonal mechanisms and marked autonomic dysfunction characterized by exaggerated sympathoexcitation and reduced parasympathetic activity. With 6 weeks of exercise training, HF‐related loss of choline acetyltransferase (ChAT)‐positive vagal preganglionic neurones is avoided, restoring the parasympathetic tonus to the heart, and the immunoreactivity of dopamine β‐hydroxylase‐positive premotor neurones that drive sympathetic outflow to the heart is reduced. Training‐induced correction of autonomic dysfunction occurs even with the persistence of abnormal ventricular function. Strong positive correlation between improved parasympathetic tonus to the heart and increased ChAT immunoreactivity in vagal preganglionic neurones after training indicates this is a crucial mechanism to restore autonomic function in heart failure. Exercise training is an efficient tool to attenuate sympathoexcitation, a hallmark of heart failure (HF). Although sympathetic modulation in HF is widely studied, information regarding parasympathetic control is lacking. We examined the combined effects of sympathetic and vagal tonus to the heart in sedentary (Sed) and exercise trained (ET) HF rats and the contribution of respective premotor and preganglionic neurones. Wistar rats submitted to coronary artery ligation or sham surgery were assigned to training or sedentary protocols for 6 weeks. After haemodynamic, autonomic tonus (atropine and atenolol i.v.) and ventricular function determinations, brains were collected for immunoreactivity assays (choline acetyltransferase, ChATir; dopamine β‐hydroxylase, DBHir) and neuronal counting in the dorsal motor nucleus of vagus (DMV), nucleus ambiguus (NA) and rostroventrolateral medulla (RVLM). HF‐Sed vs. SHAM‐Sed exhibited decreased exercise capacity, reduced ejection fraction, increased left ventricle end diastolic pressure, smaller positive and negative dP/dt, decreased intrinsic heart rate (IHR), lower parasympathetic and higher sympathetic tonus, reduced preganglionic vagal neurones and ChATir in the DMV/NA, and increased RVLM DBHir. Training increased treadmill performance, normalized autonomic tonus and IHR, restored the number of DMV and NA neurones and corrected ChATir without affecting ventricular function. There were strong positive correlations between parasympathetic tonus and ChATir in NA and DMV. RVLM DBHir was also normalized