Electrical properties of the nexal membrane studied in rat ventricular cell pairs

Cell pairs isolated from adult rat ventricles were used to characterize the electrical properties of the nexal membrane located between the cells. Each cell of a cell pair was connected to a suction pipette so as to enable whole-cell recordings. A double voltage-clamp method was employed which allowed the voltage gradient across the nexal membrane to be controlled. The current-voltage relationship of the nexal membrane was found to be linear over a broad range of transnexal voltages ( +/- 50 mV). The measurements revealed a mean value for the apparent nexal membrane resistance, rn(app), of 3.4 M omega. Taking into account the contribution of an uncompensated series resistance (access resistance), the effective nexal resistance, rn(eff), amounts to 1.7 M omega, approximately. The nexal membrane resistance was found to be insensitive to the sarcolemmal membrane potential, Vm (voltage range tested: -90 mV to +30 mV). The nexal membrane showed no rectifying property, i.e. it allows impulse transmission in both directions equally well. The connexons of the nexal membrane exhibited no time-dependent gating behaviour (time range investigated: 0.1-10 s).