Cardiac autonomic balance in rats submitted to protein restriction after weaning.
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2011
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Resumo
1. In the present study, we evaluated the autonomic balance of
the heart in protein ⁄ energy-undernourished rats.
2. Rats were divided into two groups according to the diet they
received after weaning: (i) the control group (n = 16), given a
15% protein diet, and (ii) the malnourished group (n = 14), fed a
6% protein diet. Cardiovascular recordings were made and,
through selective autonomic blockade, the tonic autonomic balance,
cardiac autonomic index and the power spectrum of heart
rate (HR) variability were determined.
3. Muscarinic receptor blockade with methylatropine
(5.0 mg⁄ kg, i.v.) increased HR in the control group (371 ± 6 vs
427 ± 15 b.p.m. before and after drug administration, respectively),
but not the malnourished group (438 ± 24 vs
472 ± 38 b.p.m. before and after drug administration, respectively).
Inhibition of b1-adrenoceptors with metoprolol
(2.0 mg⁄ kg, i.v.) reduced HR in malnourished rats (428 ± 24 vs
355 ± 16 b.p.m. before and after drug administration, respectively),
but had no effect on the HR of the control group (363 ± 8
vs 362 ± 7 b.p.m. before and after drug administration, respectively).
Double autonomic blockade by inhibiting both muscarinic
cholinoceptors and b1-adrenoceptors reduced HR in the
malnourished group (428 ± 24 vs 342 ± 14 b.p.m.) but had no
effect on HR in the control group (371 ± 6 vs 382 ± 6 b.p.m.).
4. Sympathetic tone was augmented in malnourished compared
with control rats (131 ± 17 vs 41 ± 11 b.p.m., respectively),
whereas parasympathetic tone was reduced in malnourished
compared with control rats (–4 ± 4 vs 22 ± 9 b.p.m., respectively).
5. The ratio of oscillations in HR induced by sympathetic and
parasympathetic activity was higher in malnourished compared
with control rats (0.43 ± 0.03 vs 0.34 ± 0.02, respectively).
6. The results of the present study indicate that protein malnutrition
after weaning increases sympathetic activity and reduces
vagal activity to the heart in rats. These data provide a new perspective
on the pathophysiology of metabolic and cardiovascular
diseases associated with protein malnutrition, especially with
regard to autonomic modulation.
Key words: autonomic index, intrinsic heart rate, malnutrition,
parasympathetic, power spectrum, rats, sympathetic.
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Autonomic index, Intrinsic heart rate, Malnutrition, Parasympathetic, Power spectrum, Sympathetic
Citação
MARTINS, C. D. D.; CHIANCA JÚNIOR, D. A.; FERNANDES, L. G. Cardiac autonomic balance in rats submitted to protein restriction after weaning. Clinical and Experimental Pharmacology & Physiology , v. 38, p. 89-93, 2011. 1803. Disponível em: <http://onlinelibrary.wiley.com/doi/10.1111/j.1440-1681.2010.05468.x/abstract>. Acesso em: 19 fev. 2017.