VOLTAGE CLAMP ON HELIX POMATIA NEURONAL MEMBRANE - CURRENT MEASUREMENT OVER A LIMITED AREA OF SOMA SURFACE

A method was developed, to measure during a voltage clamp the current which flows through a limited area (104 μ2) of the soma membrane. In addition to an intracellular voltage clamp electrode, a fire-polished glass micropipette is placed on the soma surface (with slight suction applied), and only the clamp current through the pipette is measured. This measurement excludes uncontrolled currents from the axon. Alternatively the membrane spot" (area under the pipette) can be voltage clamped while the rest of the cell is kept in the resting state. The latter method is an advantage with bigger cells where homogeneous clamp over the whole surface cannot be achieved. © 1969 Springer-Verlag."