title: Electrical stimulation of the aortic depressor nerve in conscious rats overcomes the attenuation of the baroreflex in chronic heart failure.
abstract: Chronic heart failure (CHF) is characterized by autonomic dysfunction combined with baroreflex attenuation. The hypotensive and bradycardic responses produced by electrical stimulation of the aortic depressor nerve (ADN) were examined in conscious CHF and control male Wistar rats (12-13 wk old). Furthermore, the role of parasympathetic and sympathetic nervous system in mediating the cardiovascular responses to baroreflex activation was evaluated by selective β1-adrenergic and muscarinic receptor antagonists. CHF was induced by myocardial infarction. After 6 wk, the subjects were implanted with electrodes for ADN stimulation. Twenty-four hours later, electrical stimulation of the ADN was applied for 20 s using five different frequencies (5, 15, 30, 60, and 90 Hz), while the arterial pressure was recorded by a catheter implanted into the femoral artery. Electrical stimulation of the ADN elicited progressive and similar hypotensive and bradycardic responses in control (n = 12) and CHF (n = 11) rats, while the hypotensive response was not affected by methylatropine. Nevertheless, the reflex bradycardia was attenuated by methylatropine in control, but not in CHF rats. Atenolol did not affect the hypotensive or bradycardic response in either group. The ADN function was examined under anesthesia through electroneurographic recordings. The arterial pressure-ADN activity relationship was attenuated in CHF rats. In conclusion, despite the attenuation of baroreceptor function in CHF rats, the electrical stimulation of the ADN elicited a stimulus-dependent hypotension and bradycardia of similar magnitude as observed in control rats. Therefore, electrical activation of the aortic baroreflex overcomes both the attenuation of parasympathetic function and the sympathetic overdrive.
authors: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil;
authors: Tomás O C Teixeira
authors: TO
authors: Pinto
authors: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil;
authors: Renata M
authors: RM
authors: Lataro
authors: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil;
authors: Jaci A
authors: JA
authors: Castania
authors: Department of Medicine, University of Ribeirão Preto, Ribeirão Preto, São Paulo, Brazil; and.
authors: Marina T
authors: MT
authors: Durand
authors: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil;
authors: Carlos A A
authors: CA
authors: Silva
authors: Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska.
authors: Kaushik P
authors: KP
authors: Patel
authors: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil;
authors: Rubens
authors: R
authors: Fazan
authors: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil; hcsalgado@fmrp.usp.br.
authors: Helio C
authors: HC
authors: Salgado
mesh_terms: D000818:Animals; D001011:Aorta / Q000294:innervation*; D017704:Baroreflex; D001794:Blood Pressure; D004599:Electric Stimulation Therapy / Q000379:methods; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy*; D006339:Heart Rate; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods*; D016896:Treatment Outcome
keywords: aortic depressor nerve; baroreflex activation; electric stimulation; heart failure