نقش پمپ سدیم - پتاسیم وابسته به انرژی در اثرات عصاره هیدروالکلی ریشه گزنه بر روی گره دهلیزی بطنی جدا شده خرگوش نر

Background and Purpose: Previous studies have demonstrated the cardiovascular effects of Urtica dioica (Nettle) such as anti-hypertensive, and negative inotropic effects on heart . The effects of plant on atrioventricular node has not been explored yet.Inhibitory Na+-K+-ATPas pump has been shown ny U. dioica . The aims of the present study were: 1) to determine concentration-dependent effects of ethanolic extract of nettle on the nodal basic and functional properties. 2) to campare mechanism of action nettel with ouabaine and verapamil. Materials and Methods: This was an experimental study. Male New Zealand rabbits (1-1.3 kg) were used in all of the experiments Various experimental stimulating protocols (Wbcl Recovery, Facilitation, Fatigue) were applied to assess electrophysiological properties of Node. We used isolated perfused AV-nodal preparation (n=18). All protocols were repeated in the presence and absence (control) of different concentration (0.2-0.4 g/l) of Nettle, verapamil (0.1μM) and ouabaine (0.25μM). Results were shown as Mean ± SE and a probability of 5% was used to indicate statistical significance. Results: In the presence of Nettel, significant increases in WBCL (150.7± 4.3 to 180 ±15.2msec), AVCT (44±2.5 to 54±1.7msec), ERP (125±13 to 149 ±20.6msec) and magnitude of fatigue (ΔAH) 6 ± 0.9 msec were observed. The nettel has less inhibitory activity than verapamil, such as ERP of Nettel was 40% of verapamil. Also, Nettel had similar electrophysiological effects in regard to ouabain. Conclusion: In the present study, negative dormotropic effect of extract, Citrus bigaradia of Nettel, was observed on the isolated AV-nodal preparation. The same electrophsiological trend of ouabain and Nettel, may indicate the role of Na+-K+-ATPas pump in the deppresant effect of Nettel.