The present study investigated the effects of rotigaptide (ZP123) on the expression, distribution and phosphorylation of connexin43 (Cx43) in myocardial cell membranes in cardioversion of ventricular fibrillation (VF). A model of prolonged VF (8, 12 and 30 min) was established in mongrel dogs (n= 8/group), following treatment with ZP123 or normal saline (NS control). A sham control was included. Cardiopulmonary resuscitation was begun at the start of VF followed by defibrillation. Animals received a maximum of three defibrillations of increasing energy (70, 100 and 150 J biphasic shock) as required. The average defibrillation energy, defibrillation success rate, return of spontaneous circulation and survival rate were recorded. Cx43 and phosphorylated (p-) Cx43 expression in cardiomyocyte membranes was detected by western blot and immunofluorescence analyses. Compared with the NS-treated control groups, the success defibrillation rate in the 8-min and 12-min ZP123 groups was significantly higher (P< 0.05), while the average defibrillation energy was significantly lower (P< 0.05). Cx43 expression in the VF groups was significantly lower than that in the sham control group (P< 0.05). Cx43 expression was higher in the 12-min and 30-min ZP123 groups than that in the NS control group (P< 0.05), while p-Cx43 expression decreased, although the levels were significantly higher than those in the control groups (P< 0.05). Cx43 expression was positively correlated with the defibrillation success rate (r= 0.91; P< 0.01) and negatively with the mean defibrillation energy (r=-0.854; P< 0.01), while p-Cx43 expression was positively correlated with the success rate of the previous three defibrillations (r= 0.926; P< 0.01). In conclusion, ZP123 reduced Cx43 remodeling through regulating the expression, distribution and phosphorylation of Cx43, thereby reducing the defibrillation energy required for successful cardioversion.