Gerald Pollack, Gels, Cells, Biology, Biophysics.
(page 251). The next big advance was patch-clamp recording (Neher and Sakmann 1976). Micropipettes were sealed against a cell membrane that had been cleaned of connective tissue by treatment with enzymes. A very-high-resistance seal resulted [(2–3)×10^7Ω] that allowed one to see the opening and