Figure 4. Single channel activity of a cell pair whose gap junction contained a single channel.

A, sister current records documenting the de novo formation of a gap junction channel. V_j was maintained at -40 mV. Simultaneous transitions in I₁ and I₂ reflect gap junction events (channel opening: upward deflections in I₁, downward deflections in I₂). The very first transition was slow and corresponds to the first opening after channel formation. The subsequent transitions were fast and represent channel flickering between the main state and the residual state (dashed lines). Continuous lines indicate the zero coupling current. B, single channel currents from a weakly coupled cell pair elicited by V_j pulses (V₁ and V₂) of 50 mV (top and middle I₁ trace) and 75 mV (bottom I₁ trace). The coupling currents in the presence of one (top and middle I₁ trace) and two channels (bottom I₁ trace) exhibited fast transitions between the main state and the residual state.