Modeling Ion Channels in the Gigaseal

AbstractThe ability to form gigaseals is essential for patch-clamp electrophysiology; however, ion channels located in the seal can produce measureable currents. To explore the expected properties of channels in the seal (i.e., rim channels), we created a mathematical model. The seal was a two-dimensional cable filled with saline and bounded on one side by membrane (with resistance and capacitance) and on the other side by glass (nonconductive and noncapacitive). We included ion depletion/accumulation around the channels. The channels were ohmic with a conductance that increased with the concentration of permeant ions. The aqueous seal thickness was set nominally to 1 nm. Imaging with fluorescent dyes in the pipette showed that the hydrophilic dye Alexa 488 is impermeant, but lipophilic FM1-43 labels the seal. The model showed that to obtain high-resistance seals, the conductivity of the seal media has to be