Connexin 43 is a connexin gap junction found in several organs and cell types, but is most often found in the heart. Current data suggest Cx43 is essential for the development of normal cardiac architecture and ventricular conduction. Two members of the connexin gene family, connexins 43 and 32, or GJB1, are abundantly expressed in the heart and liver, respectively. Li et al. (1995) demonstrated that GAP43-like immunoreactivity in rat is mainly present in sympathetic and sensory nerve fibers as well as in perivascular nerve terminals. This peptide is axonally transported predominantly in sensory and adrenergic axonsSohl et al. (2003) stated that the mouse and human CX43 share 97% amino acid identity. Northern blot analysis detected variable expression of a 3.0-kb CX43 transcript in both mouse and human, with highest expression in heart.