ABSTRACT
Amoebae can be penetrated by microelectrodes at either end. One records voltage and the other supplies alternating current.
Step-like increases in alternating voltage superimposed on potentials recorded by the voltage electrode when in either the pseudopod or rear region demonstrate that low potentials recorded from a pseudopod and high ones from the rear region exist across a discrete impedance barrier. The only structure so far shown to fulfil this function is the plasma membrane.
A resistance inserted in the earth path monitors current flowing through the system and confirms observations made when recording with single electrodes that there is a reduction of electrode resistance when the cell is entered.
Pronounced depolarization in the rear region is shown when the currentcarrying electrode penetrates the pseudopod, but not vice versa.
Morphological changes associated with membrane potential reversal are illustrated.
Consideration is given to the role of step-like potential changes in movement.
