Role of vagal activity on bradicardic and hypotensive effects of caffeic acid phenethyl ester (CAPE)

Caffeic acid phenethyl ester (CAPE) is a phenolic active component of propolis of honeybee hives and reduces heart rate and blood pressure in rats. The objective of this study was to investigate the role of vagal activity and atropine blockage on the bradycardic and hypotensive effects of CAPE in rats. The rats were divided into five groups (n = 8). Saline and vehicle (10% ethanol) of CAPE were given to the first and second groups, respectively. Group 3 was treated with 5 mg/kg CAPE. Group 4 bivagotomized and treated with 5 mg/kg CAPE. Group 5 treated with atropine (5 microg/microL/min) continuously and treated with CAPE. The electrophysiological monitoring was done for each experiment under urethane anesthetize. As a result, CAPE caused intense and transient bradycardia and hypotension. Vagotomy completely abolished bradycardia occurred via CAPE injection; however atropine attenuated bradycardic effects of CAPE. On the other hand, hypotensive effect of CAPE was affected from neither bilateral vagotomy nor atropine treatment. It was thought that CAPE may exert its effects on heart rate via a central parasympathetic control mechanism, but not on central parasympathetic blood pressure control system.