New techniques for the study of lens electrophysiology

The development of the gigohm seal patch clamp has extended the use of the voltage clamp technique to cells too small to study with more conventional approaches. We report the application of this technique, in its many configurations, to the study of lens epithelial cells. The technique allows measurement of membrane current at the microscopic (single channel) level or at the macroscopic (whole cell) level. At the single channel level, three configurations (on-cell, inside-out, and outside-out) are standard. The advantages and disadvantages of each are discussed. A more novel configuration, the on-cell whole-cell configuration, has several advantages over these more traditional patch configurations. Measurement of current from the entire cell membrane under voltage clamp can be achieved with the whole cell variant of the patch clamp technique. Two less invasive versions of this procedure (the perforated patch technique and droop analysis) are presented. Finally, the extension of the whole cell technique to a pair of dissociated cells is shown to allow the measurement of currents flowing through gap junctions. For each case, data is presented from lens epithelial cells (from frog, chick, rabbit and human).