Criteria for perforated-patch recordings: ion currents versus dye permeation in human T lymphocytes

Nystatin-perforated patches are now frequently used to help preserve cytoplasmic integrity during patch-clamp recordings. We used voltage-dependent K+ currents in human T lymphocytes to compare conventional whole-cell recordings with perforated-patch recordings (PPR). Although there were pronounced differences in the inactivation kinetics, we discovered that our PPR recordings were not "intact". In every case, coinciding with the gradual capacitance transient increase and decrease in access resistance, we observed that large (> MW 800) fluorescent dyes enter the cell from the pipette. These results suggest that caution is required when using differences in the properties of the currents to confirm that the nystatin-containing patch is intact.