Cardiac sympathetic-parasympathetic balance in rats with experimentally-induced acute chagasic myocarditis O balanço autonômico cardíaco nas ratas com miocardite chagásica aguda experimental

• Published in: Revista do Instituto de Medicina Tropical de São Paulo
• Main Authors: Diego F. Davila, Carlos F. Gotterberg, Argenis Torres, Geza Holzhaker, Richard Barrios, Paolo Ramoni, José H. Donis
• Format: Article in Journal/Newspaper
• Language: English
• Published: Universidade de São Paulo (USP) 1995
• Subjects: Myocarditis; Chagas disease; Cardiac Autonomic System; Atropine; Beta-Blockers; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Aguda; Arctic
• Online Access: https://doi.org/10.1590/S0036-46651995000200011; https://doaj.org/article/89bd8ab7beed42b891540136fe09d5d5

To clarify the mechanism responsible for the transient sinus tachycardia in rats with acute chagasic myocarditis, we have examined the cardiac sympathetic-parasympathetic balance of 29 rats inoculated with 200,000 parasites (Trypanosoma cruzi). Sixteen infected animals and 8 controls were studied between days 18 and 21 after inoculation (acute stage). The remaining 13 infected animals and 9 controls were studied between days 60 and 70 after inoculation (sub-acute stage). Under anesthesia (urethane 1.25 g/kg), all animals received intravenous atenolol (5 mg/kg) and atropine (10 mg/kg). Acute stage: The baseline heart rate of the infected animals was significantly higher than that of the controls (P < 0.0001). The magnitude of the negative chronotropic response to atenolol was 4 times that of the controls (P < 0.00001). This response correlated with the baseline heart rate (r= - 0.72, P < 0.001). The heart rate responses to the beta-blocker and to atropine, of the infected animals studied during the sub-acute stage, were not different from controls. These findings suggest that cardiac sympathetic activity is transiently enhanced and cardiac parasympathetic activity is not impaired, in rats with acute chagasic myocarditis. The transient predominance of cardiac sympathetic activity could explain, in part, the sinus tachycardia observed in the acute stage of experimentally-induced chagasic myocarditis. Com a finalidade de pesquisar o mecanismo responsável pela taquicardia sinusal transitória que ocorre nas ratas com miocardite chagásica aguda, foi estudado o balanço autonômico cardíaco em 16 ratas inoculadas com Trypanosoma cruzi por via intraperitoneal. Oito animais foram estudados aos 18 e 21 dias após-inoculação (Estádio agudo); os oito animais restantes foram estudados entre os dias 60 a 70 após inoculação (Estádio sub-agudo). Todos os animais em estudo bem como os controles receberam atenolol e atropina. No estádio agudo, a frequência cardíaca basal dos animais infectados foi significativamente maior ...