Effects Of ACH/ISO On Atrial Dispersion Of Atrial Refractory Period In Isolated Heart In Mice

Background: The autonomic nerve system plays an important role in the mechanism of atrial fibrillation .Stimulation of the autonomic nerve results in the shortening of atrial effective refractory period(ERP) and decreasing in the reentrant wavelength. However, the characteristic of atrial electric properties in isolated heart in mice is poorly understood . The purpose of this study is to investigate the changes of the atrial action potential duration(APD) and the dispersion of ERP(dERP) in response to acetylcholine/ isoproternol (Ach/Iso) and the mechanism underlying the atrial fibrillation.Purpose: This study is to investigate the changes of the atrial action potential duration(APD) and the dispersion of ERP(dERP) in response to Ach/Iso in the isolated atria in mice .Method : 17 mice were involved in this study. The standard glass microelectrode technique was used to record the APD at 90% repolarization level (APD90), the ERP(the longest S1S2 interval failing to capture the atrium ) in the left atrum(LA), left atrial appendage(LAA), right atrum(RA), and right atrial appendage(RAA) under the baseline, acetylcholine (1μmol/L) and isoproterenol (10μmol/L)perfusion, respectively. Result : (1) APD90:In control group, the APD90 recorded in the tissue from LAA and LA are shorter than RAA and RA(LAA71.2±6.83ms VS LA77.29ms VS RA 86.63 ±5.46ms VS RA83.56±6.74ms,p<0.05)。in Iso group, the APD90 in LAA are shorter than that in RAA(66.53±3.28ms VS 74.8 ±4.88ms,p<0.05). In Ach group, the APD90 in LAA are larger than that in RAA and RA(LAA41.32±4.08ms VS RAA32.53 ±4.69ms VS RA36.1 ±6.26ms,p<0.05).(2) ERP: in control group, LAA and LA tissue have shorter ERP than the RAA and RA tissue(LAA77.7±4.65ms VS LA85.23ms VS RAA 92.1±4.86ms VS 89.6 ±4.85ms,p<0.05)。In Iso group, the ERP in LAA are less than that in RAA (69.06±4.1ms VS 76.6±6.48ms,p<0.05)。In Ach group, the ERP in LAA are longer than that in RAA and RA (LAA 43.68±4.33ms VS RAA 32.31±4ms,p<0.05 ).(3) dERP: dERP is 15.96±6.73ms in control group, 13.73 ±4.61ms in Iso group, 13.27±3.17ms in Ach group。There is no significant difference in three groups (p>0.05)。Conclusion : There is repolarizatin ununiformity between the two atria in mice . The APD90 and ERP are shortened when the atrium tissues are perfused with Ach and Iso. Ach shortens the APD90 and ERP more obviously in the right atrium more than the left atrium.