Relation Between Vagus Nerve And Remodeling Of Gap Junction In Superior Vena Cava Myosleeve In Canine With Atrial Fibrillation

Objectives To investigate the relationship between cardiac vagus nerve 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 bpm for 6 weeks to establish AF model. AF was induced by programmed stimulation or burst stimulation of atrial pacing. Cx40 and Cx43 in the SVC myosleeve tissue in three groups were labeled by FITC resopectively. The distributions of Cx40 and Cx43 in three groups were analyzed by fluorescent microscope and the expressions of them were quantitated by Image Pro Plus 6.0 image analysis system. Moreover, fresh tissue of SVC myosleeve were fixed by stationary liquid and the ultrastructural organization of gap junction(GJ) was observed by transmission electron microscope. Results (1) Sustained AF could be induced in five of seven dogs in RS group, but none of dogs had been induced sustained AF in RM group. (2)The expression of Cx40 and Cx43 in Sham group and RS group wrere significantly higher than that in RM group(P<0.05). Furthermore, the expression of Cx40 and Cx43 in RS group were obviously higher than that in Sham group(P<0.05). The distribution of Cx40 and Cx43 in side-to-side of GJ in RS group were significantly higher than that in Sham group and RM group(P<0.05). But the distribution of Cx40 and Cx43 in side-to-side of GJ in RM group were obviously higher than that in Sham group(P<0.05). (3) Comparing with Sham group, the channel of GJ became shorter and wider in RS group(P<0.05). In RS group, sarcomere was dissolved, mitochondrion showed vacuole degeneration, glycogen accumulated, and intercalated disc was tortuous. But the change of ultrastructural organization of GJ in RM group was between Sham group and RS group.Conclusions (1) The increasing of Cx40, Cx43 and the remodeling of gap junction may be mediated by vagus nerves in superior vena cava myosleeve in canine. However, these changes can be weakened by removing SVC-AO fat pad of canine. (2) The remodeling of connexin and gap junction 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.