Abstract: Objective To investigate the relationship between cardiac vagus nerves and changes of connexins(Cx) and intracellular gap junction(GJ) distribution pattern in superior vena cava(SVC) myosleeve in canine with atrial fibrillation(AF). Methods Twenty four hybrid dogs were divided into sham operation group(Sham group,n=8),SVC-AO fat pad removed group(RM group,n=8) and SVC-AO fat pad reserved group(RS group,n=8).In RM group and RS group, right atrial pacing was performed at a frequency of 500-650/min for 6 weeks to establish AF model. AF was induced by programmed stimulation or burst stimulation of atrial pacing. The expression and distribution of Cx40, Cx43 in the SVC myosleeve tissue in three groups were analyzed by immunofluorescence staining. Transmission electron microscope was used to observe the ultrastructural organization of gap junction(GJ). Results The rate of inducing sustained AF(>15minutes) in RS group was significantly higher than that in RM group(P＜0.01). The expression of Cx40, Cx43 in the SVC myosleeve in sham group and RS group were significantly higher than that in RM group(P＜0.05). Furthermore, the expression of Cx40, Cx43 in RS group were obviously higher than that in sham group(P＜0.05). The ratio of end-to-end to side-to-side in RS group was lower than that in Sham group and RM group. Comparing with RM group, the channel of GJ became shorter and wider in RS group(P＜0.05). Sarcomere was dissolved and mitochondrion showed vacuole degeneration in RS group. Conclusions The remodeling of Cx40, Cx43 in SVC myosleeve tissue may be mediated by vagus nerves. It is conducive to the maintenance and stability of AF. However, this effect can be weakened by removing SVC-AO fat pad of canine.

Key words: Vagus nerves, Atrial fibrillation, Connexin, Fat pad