Voluntary exercise does not affect stress-induced tachycardia, but improves resistance to cardiac arrhythmias in rats


Autoria(s): Beig, Mirza I.; Callister, Robin; Saint, David A.; Bondarenko, Eugene; Walker, Frederick R.; Day, Trevor A.; Nalivaiko, Eugene
Data(s)

01/01/2011

Resumo

1. It is currently unknown whether long-term voluntary exercise has enduring cardioprotective effects in animal models.<br /><br />2. The present study was conducted in three groups of rats: (i) sedentary controls (n = 6); (ii) 24 h runners (n = 8; unlimited access to running wheels); and (iii) 2 h runners (n = 8; access to running wheels limited to 2 h daily). After termination of the 6 week exercise protocol, all rats were implanted with the telemetric electrocardiogram transmitters and were studied 1 week later.<br /><br />3. Resting heart rate (HR) values in the control rats, 24 h runners and 2 h runners were 372 ± 7, 361 ± 9 and 298 ± 5 b.p.m., respectively (P < 0.05 for 2 h runners vs controls). The high-frequency spectral power in the control rats, 24 h runners and 2 h runners was 3.9 ± 0.2, 4.3 ± 0.3 and 5.3 ± 0.3 s2, respectively (P < 0.05 for 2 h runners vs controls), whereas intrinsic HR was 383 ± 3, 377 ± 2 and 346 ± 3 b.p.m., respectively (P < 0.001 for 2 h runners vs controls). Restraint stress provoked tachycardia of similar magnitude in all groups.<br /><br />4. After completion of telemetric studies, haemodynamic indices and susceptibility to cardiac arrhythmias were assessed in anaesthetized animals, there were no major between-group differences in HR, arterial pressure, contractility indices or sensitivity to β-adrenoceptor stimulation (dobutamine) or blockade (atenolol). The effective refractory period in the control rats, 24 h runners and 2 h runners was 49 ± 2, 55 ± 2 and 60 ± 4 ms, respectively (P = 0.054 for 2 h runners vs controls). A significantly higher dose of aconitine was required to provoke ventricular arrhythmias in the 24 h and 2 h running groups compared with controls (489 ± 76, 505 ± 88 and 173 ± 33 μg, respectively; P < 0.05).<br /><br />5. We conclude that, in rats, long-term voluntary exercise has enduring cardioprotective effects mediated at the level of both the central nervous system and the heart.<br />

Identificador

http://hdl.handle.net/10536/DRO/DU:30044512

Idioma(s)

eng

Publicador

Wiley

Relação

http://dro.deakin.edu.au/eserv/DU:30044512/day-voluntaryexercise-2011.pdf

http://dx.doi.org/10.1111/j.1440-1681.2010.05456.x

Direitos

2010, The Authors

Palavras-Chave #heart rate #stress #ventricular arrhythmia #voluntary exercise
Tipo

Journal Article