The Effect of Ryanodine Receptor (RyR) Current Block by Ryanodine on ?Pace-making in the Rat Intact Sinoatrial and Atrioventricular Node
Trauma Monthly: 12 (3); 189-196 Article Type: Research Article
January 1, 2007
January 1, 2007
M. The Effect of Ryanodine Receptor (RyR) Current Block by Ryanodine on ?Pace-making in the Rat Intact Sinoatrial and Atrioventricular Node,
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Objective: This study was conducted to characterize the inhibitory effects of Ryanodine on pacemaker activity of the sinoatrial node (SAN) and the atrioventricular node (AVN) in rat. The method of this study was experimental and two separate metal microelectrodes were used for extracellular recording of electrical activity. The effect of ryanodine on electrical activity was studied by measuring cycle length (CL). Paired and unpaired T-student test were used for analyzing data. Inhibition of RyR by 2uM ryanodine increased CL from 283.75±27 to 412.50±82 ms on SAN and from 516.25±195 to 1570±400ms on AVN. This increase in CL is 39.50±12.8 % in SAN preparations while 186±57.50 % in AVN preparations (p< 0.05). Pacemaker activity was not stopped in none of the preparations. It is possible to conclude that: (i) The ryanodine receptor current exists in SAN & VAN. The pacemaking activity did not stop functioning in cardiac nodes after ryanodine was used, which means that the role of RyR for pacemaker activity is not obligatory.(ii) The effect of ryanodine on AVN was significantly greater than SAN that is, the role of RyR is not similar in those two nodes.
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