Efeitos cronotropico e inotropico negativos induzidos pelo timol em ratos espontaneamente hipertensos

Abstract

Thymol is a monoterpene present in the constitution of the essential oils of many plants and is well known for its broad spectrum antimicrobial activity and is also reported in the literature their activities on the cardiovascular system . Therefore , this study aimed to evaluate the chronotropic and inotropic effects induced by thymol in the SHR rats , an essential model animal of hypertension as well as in their normot ensive control WKY , by system organ technique in isolated vitro using the atria isolated from these animals. In SHR , thymol induced negative chronotropic effects ( pD 2 = 3.9 ± 0.029 ; E max = 100 ± 0 %, n = 10) and inotropic ( pD 2 = 4.6 ± 0.080 ; E max = 100 ± 0 %, n = 7). In WKY rats, the compound also induced reduction in heart rate (pD 2 = 4.0 ± 0.037; E max = 100 ± 0%, n = 5) and reduction in contractile force (pD 2 = 4.6 ± 0.058; E max = 100 ± 0%, n = 7). Both in hypertensive animals , as in normotensive animals, the negative inotropic effect showed greater power ( p < 0.001) when compared to the negative chronotropic effect . When comparing the chronotropic and inotropic effects induced by thymol in SHR and WKY rats , it was observed that the compound induced similar responses in hypertensive and normotensive animals. In conclusion, these results suggest that the effect induced by thymol on the strength of cardiac contraction is more powerful than the effect of this monoterpene on the frequency of heartbeat and that th ere is no statistical difference between normotensive and hypertensive animals in the evaluated parameters