Figure 1.

Diagram of the experimental system in which we electrically coupled two isolated sinoatrial node cells. (A) Overall experimental design in which our technique introduces a coupling conductance G _c between two patch-clamped isolated cells (cell A and cell B). (B) Simultaneous patch clamp recordings for cells A and B in the “current clamp” mode produce membrane potentials V _m,A and V _m,B, respectively, which are sampled by the computer (PC) via an A/D converter at each time step. The computer multiplies the difference in the two membrane potentials by a desired value of G _c, thus producing the equivalent I_c, which would have been present if the cells had indeed been electrically coupled. A voltage proportional to the desired I_c is output from the computer via a D/A converter and through a voltage-to-current converter (V→ I) as +I_c to cell A and through a separate set of converters as −I_c to cell B.