Electrophysiological studies of chilean squid axons under internal perfusion with sodium-rich media.

Electrophysiological properties of giant axons of Chilean squid were examined by intracellular perfusion combined with various recording techniques. The amplitude of the action potential of the axons perfused with equal sodium concentrations (0.35M) on both sides of the membrane was approximately 75 millivolts (glutamate salts being used internally); the resting potential recorded with a calomel electrode was roughly 45 mv. These observations confirm and extend previous data, obtained from Chilean squid axons, which show that the amplitude of the action-potential overshoot does not agree with the Nernst equation applied to sodium ion. The discrepancy between these results and those obtained by others is attributed to differences in the procedures used to determine the resting potential.