ABSTRACT
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. 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/1] of Nettle, verapamil [0.1 microM] and ouabaine [0.25 microM]. Results were shown as Mean +/- SE and a probability of 5% was used to indicate statistical significance. 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 [deltaAH] 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. 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