ELECTROPHYSIOLOGICAL PROPERTIES OF THE LA-PV TISSUES OF X<sub>IN</sub>-GENE KNOCKOUT MICE

Song, Chao; Lai, Yigui; Loh, Yue-Xia; Chen, Y.C.; Lin, Cheng‐I

doi:10.1142/9789812702234_0015

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“…Indeed, it is not easy to induce AF in the heart of small animals like the mouse (Garrey, 1914; Wakimoto et al, 2001; Nerbonne, 2004). However, focal AF could be induced by acetylcholine in vivo (Wakimoto et al, 2001) or by ISO in the murine LA-PV preparations (Song et al, 2005). …”

Section: Discussionmentioning

confidence: 99%

“…The rhythms were classified as automatic (spontaneously active), triggered (occurring immediately after termination of pacing) and reentrant rhythms (AF, with a frequency >18 Hz and duration >500 ms; Atienza and Jalife, 2007) as in our previous study (Song et al, 2005). …”

Section: Methodsmentioning

confidence: 99%

“…In this connection, we have shown that left atrial-pulmonary vein tissue (LA-PV) can generate AF in wild-type (mXinα+/+) but not in mXinα-deficient (mXinα-/-) mice (Song et al, 2005). This finding suggested the need to investigate the mechanism by which mXinα gene may play a role in the arrhythmias originating from the left atrial-pulmonary vein tissue.…”

Section: Introductionmentioning

confidence: 99%

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On the mechanisms of arrhythmias in the myocardium of mXinα-deficient murine left atrial-pulmonary veins

et al. 2008

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We have previously shown that left atrial-pulmonary vein tissue (LA-PV) can generate reentrant arrhythmias (atrial fibrillation, AF) in wild-type (mXinα+/+) but not in mXinα-null (mXinα-/-) mice. With the present experiments, we investigated the arrhythmogenic activity and the underlying mechanisms in mXinα+/+ versus mXinα-/-LA-PV.Electrical activity and conduction velocity (CV) were recorded in LA-PV by means of a MED64 system. CV was significantly faster in mXinα+/+ than in mXinα-/-LA-PV and it was increased by 1 μM isoproterenol (ISO). AF could be induced by fast pacing in the mXinα+/+ but not in mXinα-/-LA-PV where automatic rhythms could be present. ISO increased the incidence of AF in Xinα+/+ whereas it increased that of automatic rhythms in mXinα-/-LA-PV. In LA-PV with the right-atrium attached (RA-LA-PV), automatic rhythms occurred in all preparations. In mXinα+/+ RA-LV-PV simultaneously treated with ISO, strophanthidin and atropine, the incidence of the automatic rhythm was about the same, but AF increased significantly. In contrast, in mXinα-/-RA-LA-PV under the same condition, the automatic rhythm was markedly enhanced, but still no AF occurred. Conventional microelectrode techniques showed a longer APD 90 and a less negative maximum diastolic potential (MDP) in mXinα-/-than mXinα+/+ LA-PV tissues. Whole-cell current clamp experiments also showed a less negative MDP in mXinα-/-versus mXinα+/+ LA-PV cardiomyocytes.The fact that AF could be induced by fast pacing under several conditions in mXinα+/+ but not in mXinα-/-LA-PV preparations appears to be due to a slower CV, a prolonged APD 90 , a less negative MDP and possibly larger areas of conduction block in mXinα-/-myocardial cells. In contrast, the non-impairment of automatic and triggered rhythms in mXinα-/-preparations may be due to the fact that the mechanisms underlying these rhythms do not involve cell to cell conduction.

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