Gap junction modifiers regulate electrical activities of the sinoatrial node and pulmonary vein: Therapeutic implications in atrial arrhythmogenesis

Background: Gap junction (GJ) dysfunctions predispose cardiac tissues to various arrhythmias. Sinoatrial node (SAN) and pulmonary veins (PVs) are closely related atrial dysrhythmia. This study evaluated whether GJ modifications modulate SAN and PVs electrical activities. Methods: Conventional microelectrodes were used to record action potentials in isolated rabbit SAN, PVs, and connected PV-SAN tissue preparations before and after heptanol (GJ inhibitor) and PQ1 (GJ enhancer) administration with and without isoproterenol. A whole-cell patch clamp was used to record the electrical activities before and after heptanol in single SAN and PV cardiomyocytes. Results: Heptanol (1, 3, and 10 mu M) reduced the spontaneous beating rates of isolated SAN preparations but not PVs. Heptanol (10 mu M) decelerated the SAN leading rhythm in the PV-SAN preparations and induced PV burst firings without (3 of 6, 50%) and with (6 of 6, 100%) isoproterenol (1 mu M). Heptanol (10 mu M) also reduced the spontaneous beating rates in single SAN cardiomyocyte, but not PV cardiomyocyte, with a decreased pacemaker current. PQ1 (50 and 500 nM) treatment did not change the spontaneous beating rates in isolated SAN and PV preparations. In the connected PV-SAN preparations, PQ1 (500 nM) did not induce any PV firing even having additional isoproterenol treatment (1 mu M). Moreover, PQ1 (500 nM) prevented heptanol-induced electrical changes in SAN and PVs preparations. Conclusion: GJ dysfunction modulates SAN and PV electrical activity, which may contribute to atrial arrhythmogenesis. GJ enhancer has a therapeutic potential in SAN dysfunction and atrial arrhythmogenesis. (C) 2016 Elsevier Ireland Ltd. All rights reserved.