Enhancement of ventricular gap-junction coupling by rotigaptide

Aims: Rotigaptide is proposed to exert its anti-arrhythmic effects by improving myocardial gap-junction communication. To directly investigate the mechanisms of rotigaptide action, we treated cultured neonatal murine ventricular cardiomyocytes with clinical pharmacological doses of rotigaptide and directly determined its effects on gap-junctional currents. Methods and results: Neonatal murine ventricular cardiomyocytes were enzymatically isolated and cultured for 1-4 days. Primary culture cell pairs were subjected to dual whole cell patch-clamp procedures to directly measure gap-junctional currents (I_j) and voltage (V_j). Rotigaptide (0-350 nM) was applied overnight or acutely perfused into 35 mm culture dishes. Rotigaptide (35-100 nM) acutely and chronically increased the resting gap-junction conductance (g _j), and normalized steady-state minimum g_j (G _min) by 5-20%. Higher concentrations produced a diminishing response, which mimics the observed therapeutic efficacy of the drug. The inactivation kinetics was similarly slowed in a therapeutic concentration-dependent manner without affecting the V_j dependence of inactivation or recovery. The effects of 0-100 nM rotigaptide on ventricular g_j during cardiac action potential propagation were accurately modelled by computer simulations which demonstrate that clinically effective concentrations of rotigaptide can partially reverse conduction slowing due to decreases in g_j and inactivation. Conclusion: These results demonstrate that therapeutic concentrations of rotigaptide increase the resting gap-junction conductance and reduce the magnitude and kinetics of steady-state inactivation in a concentration-dependent manner. Rotigaptide may be effective in treating re-entrant forms of cardiac arrhythmias by improving conduction and preventing the formation of re-entrant circuits in partially uncoupled myocardium.