نقش رسپتورهاي آدرنرژيك در اثرات الكتروفيزيولوژيك عصاره هيدروالكلي بهارنارنج (Citrus bigaradia) در مدل آزمايشگاهي فيبريلاسيون دهليزي گره دهليزي بطني فيبريلاسيون دهليزي جدا شده خرگوش

The role ofadren0 ceptors in the electrophysiological effects of hydroalcoholic extract ofCitrus bigaradia in experimental model ofatrialfibrilation ofisolated atrioventricular node ofrabbits

Background and purpose: Preliminary studies have been established to examine the cardiotonic effect of Citru s bigaradia extract, by implenenting various mechanisms. The function al protective role of this plant against supraventricular 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. Materials and methods: In this present study, Newsland male rabb its(I.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 electrophysio logical properties of isolated rabbit AV node. In the first group (N= I0), different concentrations of hydro alcoholi c extract of Citru s bigaradia were added to thyrods to detect nodal concealed conduction. In the second group (N= 13), the effects of extracts (54-108 mgIL) were analysied in the presence of p-adereceptor blocker(Nadolol 211m). 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. Results: Citrus bigaradia, had biphasic concentration-effect pattern, such as in low and intermediate concentrations (0.8-3.2 mgIL), 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 urn) prevented the whole effects of Citrus bigaradia on the nodal conduction time, refractoriness and concealed conduction. Conclusion: The above results indicate the potential pro-arrhythmic effeets of Citrus bigaradia in worsing supraventricular taehyarrhytlunia. The effects of plant to decrea se 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 p-adrenoceptores