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Electrophysiological effects of nitric oxide on spontaneous activity of rabbit atrioventricular node cells
Author(s): 
Pages: 369-373
Year: Issue:  3
Journal: ACTA PHYSIOLOGICA SINICA

Keyword:  nitric oxideatrioventricular nodecalcium currentselectrophysiology;
Abstract: The electrophysiological effects of nitric oxide (NO) on spontaneous activity of rabbit atrioventricular (AV) node cells were examined using intracellular microelectrode technique. The results obtained are as follows. (1) NO donors sodium nitroprusside (SNP, 1 ~1000μmol/L) and 3-morpholinosydnonimine (SIN-l, 100, 1000 μmol/L) decreased the amplitude of action potential (APA), rate of spontaneous firing (RSF), velocity of diastolic (phase 4) depolarization (VDD), and maximal rate of depolarization (Vmax) in a concentration-dependent manner. (2) Pretreatment with L-type calcium channel agonist Bay K8644 (0.25 μmol/L) completely reversed the effects of SNP (100 μmol/L) on AV node cells. (3) Elevation of Ca2+ concentration (5 mmol/L) in superfusate antagonized the effects of SNP on AV node cells. (4)Perfusion with Ca2+-free K-H solution, completely abolished the effects of SNP on AV node cells. (5) Application of methylene blue (50 μmol/L), a guanylyl cyclase inhibitor, failed to abolish the inhibitory effects of SNP (100 μmol/L). All these results suggest that NO exerts a negative effect on spontaneous activity of AV node cells in rabbits. These effects are likely due to reduction in calcium influx via a cGMP-independent mechanism.
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