Non-stationary fluctuation analysis of macroscopic gap junction channel records

Non-stationary fluctuation analysis was applied to macroscopic records of junctional currents arising from homotypic Cx37 and Cx43 gap junction channels expressed in RIN cells. The data were analyzed by a modification of existing analytical methods that takes endemic uncoupling into account. The results are consistent with both channels having open probabilities ranging from 0.7 to near unity for low transjunctional voltages. The analysis also yielded estimates of single-channel conductances for the two channel types similar to those seen in single-channel recordings. The results presented here show that fluctuation analysis can be used to extract single-channel gap junctional conductances from macroscopic double whole-cell recordings. These results also constitute empirically determined estimates of the open probability that are not model-dependent.