Histological characteristics of the AV junction at different levels
Except for the connexins that dominated the electronic conduction of the heart, as labeled above, three main ion channels (Nav1.5, Cav3.1 and HCN4) participating in the depolarization of myocardial cells were immunohistochemically labeled to investigate the conduction ability in different structures.3,11,12 Figure 5A shows that Nav1.5 expression was abundant in the atrial and ventricular muscles and weak in the PB and RN, while Cav3.1 was mainly expressed in the PB and RN. Figure 5B and C shows that the CN and INE also weakly expressed Nav1.5 but positively expressed Cav3.1. Further analysis of Nav1.5 expression via immunofluorescence microscopy showed that the RN, CN and INE all presented with significantly lower Nav1.5 expression (P<0.001). No significant differences in the expression levels were observed among the RN, CN and INE (P=0.104), but there was a trend of slightly higher expression of Nav1.5 in the RN than in the other two regions.