Abstract
The purpose of the present study was to investigate whether long term low level autonomic activation can form electrophysiological substrate for atrial fibrillation (AF). In 16 anesthetized open-chest dogs, electrodes on the anterior right ganglionated plexuses (GP) and superior left GP allowed 6-h low-level GP stimulation (LL-GPS) inducing a 10% decrease in sinus rate. Similar low-level stimulation (without myocardial capture) was delivered to the myocardium remote from the GP for 6h in another 16 dogs as control group. LL-GPS: a) induced shortening of the atrial effective refractory period and increase of the window of vulnerability for AF; b) significantly increased acetylcholine-regulated potassium current (I(KACh)) at left superior pulmonary vein (LSPV) while reduced the density of L-type calcium current (I(CaL)) at LSPV and both atria, the protein expression of the channel subunit showed a consistent alteration, however both without significant changes in mRNA level. Six-hour LL-GPS induced significant changes in atrial electrophysiology and facilitated the initiation of AF, indicating that long-term low level autonomic activation would form electrophysiological substrate for AF. The underlying mechanism may be associated with a post-transcriptional regulation of increased I(KACh) and decreased I(CaL).
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