Connexin distribution and optical mapping of the mammalian av node

Atrioventricular (AV) nodal conduction and the pathways of propagation through the AV node have remained enigmatic. Histological and immunohistochemical studies have revealed distinct cellular regions within the AV node with varying distribution of specific ion channels. However, to date, there is little information concerning the pattern of localization of the gap junction proteins that mediate intercellular communication. The current immunohistochemical/confocal studies show a non-uniform distribution of three connexin isoforms (Cx 40, Cx 43 and Cx 45) within these cellular regions of the rat AV node with a marked transition from Cx 43 to Cx 40 at the compact node region. In addition, a high resolution mapping system coupled with extracellular recording electrodes was implemented during this study and has allowed for a macroscopic overview of the rabbit AV node. This approach revealed a marked delay in conduction at the area of the compact node. This information in association with the immunohistochemical studies may help to provide further insight into the mechanisms underlying the AV nodal delay