[ role of adrenoceptors in the electrophysiological effects of hydroalcoholic extract of Citrus bigaradia in experimental model of atrial fibrilation of isolated atrioventricular node of rabbits]

ABSTRACT

Preliminary studies have been established to examine the cardiotonic effect of Citrus bigaradia extract, by implenenting various mechanisms. The functional protective role of this plant against supraventricuiar tachyarrhythmia remains to be determined.The present study is designed to assess the role of hydroalcoholic extract of Citrus bigaradia by modifing the electrophysiological properties of atrioventricular node, during simulated experimental atrial fibrillation in rabbits and also, to determine the role of adrenoceptores regarding effects of Citrus bigaradia on the AV node. In this present study, Newsland male rabbits [1.5-2 kg] was used. Programmed stimulation protocols [Recovery, Wenckbach, Atrial fibrilation and Zone of concealment] were applied in two groups [N=23] to assess electrophysiological properties of isolated rabbit AV node. In the first group [N=10], different concentrations of hydroalcoholic extract of Citrus bigaradia were added to thyrods to detect nodal concealed conduction. In the second group [N=13], the effects of extracts [54-108 mg/L] were analysied in the presence of beta-adereceptor blocker [Nadolol 2 micro m]. AF protocol was simulated by high-rate atrial pacing with random coupling intervals [range 75-125 ms]. All data have been shown as Mean +/- SE. Citrus bigaradia, had biphasic concentration-effect pattern, such as in low and intermediate concentrations [0.8-3.2 mg/L], shortened nodal functional refractory period and Wenckebach. We observed a non-significant decrease in the average H-H intervals and numbers of concealed beats in all concentrations of Citrus bigaradia. Zone of concealment was shortened by this plant. Nadolol [2 micro m] prevented the whole effects of Citrus bigaradia on the nodal conduction time, refractoriness and concealed conduction. The above results indicate the potential pro-arrhythmic effects of Citrus bigaradia in worsing supraventricuiar tachyarrhythmia. The effects of plant to decrease the AV-nodal refractory period and concealment zone may be considered the major mechanism of this plant. At least some parts of effects of Citrus is mediated through beta-adrenoceptores