Disfunção Autonômica Cardíaca na Resposta Cronotrópica Barorreflexa em ratos submetidos à Desnutrição Protéica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Previous publications from our Laboratory showed that rats submitted to protein malnutrition have alterations in the sensitivity of the baroreceptor reflex. The baroreflex modulates sympathetic and parasympathetic activity in order to mantain the blood pressure homeostasis. In this work, we evaluate the sympathetic and parasympathetic components of the neurovegetative chronotropic cardiac response after barorreflex stimulation in malnourished rats. Male Fischer rats were divided in 2 groups: control (n=26) and low protein (n=26). During 35 days the control group received 15% of protein while the experimental group received 6% of protein in diet. The baroreflex sensitivity was evaluated by bolus injections of L-phenylephrine (0,25 to 4,0 mg/Kg, i.v.) or sodium nitroprusside (0,7 to 10,0 mg/Kg, i.v.) before and after the autonomic blockade. The baroreflex gain, vagal and sympathetic effect on the chronotropic response and the baroreflex latency were studied. The bradycardic index was increased in malnourished rats before autonomics blockades (-1,930,83 versus -1,640,65 bpm/mmHg) and after the atropinergic blockade (-0,440,40 versus -0,190,29 bpm/mmHg); however, it was diminished under β1-adrenergic blockade (-0,990,49 versus -1,680,74 bpm/mmHg). The tachycardic index was diminished in the low protein group (-0,900,59 bpm/mmHg versus -1,370,60 bpm/mmHg) only after atropinergic blockade. The baroreceptor reflex latency was evaluated by the interval of time between the maximum effext of the vasoatives drugs in arterial pressure and the maximum chronotropic baroreflex response. We observed increased latencies of the bradycardiac response of malnourished rats (5,704,51 versus 1,992,3s) during blockage-free situations and also under vagal blockade (15,139,91 versus 5,316,44s). The same effect was observed for the tachycardiac response under atropinergic blockade (8,256,81 versus 4,642,84s ). The vagal effect was diminished (8742 versus 12452 bpm) in rats submitted to protein restriction, while the sympathetic effect was increased in this experimental group (11142 versus 5430 bpm). The results presented in this study indicate that protein restriction can promote cardiac autonomic disfuntion in rats. Such disfuntion seems to involve an increased sympathetic activity, vagal damage and a delay in the activation of the baroreceptor reflex.

ASSUNTO(S)

bioquimica 1. desnutrição - teses. 2. batimento cardíaco - teses. 3. disfunção cerebral mínima - teses.

ACESSO AO ARTIGO

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