Avaliação dos efeitos cardiovasculares induzidos pelo extrato metanólico da Cecropia pachystachya

Abstract

Cecropia pachystachya (Cecropiaceae) is a medicinal plant known as "Embaúba". It is traditionally used to treat diabetes, cough and asthma, in addition to being used as an anti-inflammatory, diuretic and cardiotonic agent. Studies prove several biological activities for this species, among them, hypotensive effect in normotensive rats. Thus, the objective of this work was to evaluate the hypotensive and bradycardic effect of the methanolic extract of C. pachystachya (EMCP) in spontaneously hypertensive rats (SHR). For that, protocols for direct measurement of blood pressure and heart rate were performed in non-anesthetized SHR rats. In addition, atropine and L-NAME blockers were used to evaluate the participation of muscarinic and nitric oxide (NO) receptors, respectively, in the effect. In conscious SHR rats, MECP (0.5; 1; 5; 10; 20 and 30 mg.kg-1 iv) produced hypotension (-4.0±0.5; -5.8±0.5; -10.1±0.9; -11.4±2.1; - 29.6±4.9 and -35.7±5.3 %) and bradycardia (6.7±1.7; -3.2±2.8; -4.2±2.7; 4.1±2.1; - 67.2±2.2 and -74.0±2.5 %). After blocking with atropine, a non-selective inhibitor of muscarinic receptors, hypotension was attenuated and reversed in the last two doses (0.3±1.1; -3.1±3.4; -2.9±2.7; -10.1±1.8; 31.8±0.2; 35.6±4.1 %), as well as a reversal of the bradycardic effect (-5.4±3.6; 0.9±2,0; 0.0±3.4; 4.7±1.7; 4.2±2.3 and 4.9±1.1 %). After pretreatment with L-name, a NOS inhibitor, the hypotensive effect was attenuated only at the dose of 20 mg.kg-1 (-3.2±0.2; -1.9±0.7; -5,8±1.4; -10.3±5.5; -17.8±3.5; - 29.2±10.8 %), associated with bradycardia (4.0±1.0; 2.1±2.3; -22.0±3.0; -23.8±9.3; - 61.7±6.2; -72.6±1.9 %). It is concluded, therefore, that EMCP promotes hypotensive and bradycardic effects in SHR rats and these effects seem to be related to activation of endothelial and cardiac muscarinic receptors.