Possible mechanism of inotropic and chronotropic effects of Rosa damascena on isolated guinea pig heart

Background: The possible mechanism(s) of inotropic and chronotropic effects of the extract from Rosa damascena (R. damascena) on heart was examined. Methods: Inotropic and chronotropic effects of four concentrations of the extract from R. damascena and isoprenaline were examined in isolated guinea-pig hearts perfused through aorta in a Langendorff model. All measurements were performed in three different groups: 1) In the presence and absence of propranolol, 2) In the presence and absence of methacholine and 3) In the presence of diltiazem (n = 12 for each group). Results: In all groups both isoprenaline and the extract caused an increase in heart rate and contractility (p 0.05 to p 0.001). Only in group 1, the final concentration of isoprenaline in the absence of propranolol caused significant greater increase in heart rate compared to the extract (207.6 ± 11.0 compared to 162.6 ± 11.8, p 0.01). The percent increase in heart contractility due to the final concentration of the extract in the absence (362.4 ± 36.9 compared to 227.7 ± 31.6, p 0.01) and presence of propranolol (577.1 ± 62.9 compared to 357.5 ± 45.6, p 0.001) in group 1 and absence (403.7 ± 42.1 compared to 244.8 ± 18.9, p 0.005) and presence of methcholine (499.88 ± 64.64 compared to 323.90 ± 44.49, p 0.05) in groups 2 was significantly greater than the increase caused by isoprenaline. Conclusions: The results of this study suggest that inotropic and chornotropic effect of R. damascena is possibly due to the stimulatory effect of this plant on beta-adrenoceptors.