Voltage gating of Cx43 gap junction channels involves fast and slow current transitions.

RIN cells transfected with mouse cDNA coding for connexin43 (Cx43) were used to further examine the electrical properties of single gap junction channels. The experiments involved measuring intercellular currents from cell pairs using dual whole-cell recording with the patch-clamp method. We found that the single-channel currents exhibit two types of transitions and several conductance states. Besides fast transitions between the main open state and the residual state, the channels underwent slow transitions between an open state (i.e. main open state or residual state) and a closed state. The fast transitions lasted less than 2 ms, the slow ones ranged from 3.5 to 145 ms. The incidence of slow transitions increased with increasing transjunctional voltage. These observations are consistent with the notion that Cx43 gap junction channels possess more than one mechanism of voltage gating.