Membrane Conductance and Current-Voltage Relation in the Squid Axon Under ‘Voltage-Clamp’

¹ From the Laboratory of Neurophysiology, National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland

The conductance of the squid axon membrane under ‘voltage-clamp’ was measured by superposing a sinusoidal wave upon rectangular clamping voltage pulses. It was possible to determine the time course of the emf of the membrane under ‘voltage-clamp’ on a single photographic record showing the membrane current together with the simultaneously recorded membrane conductance. The properties of the membrane in the mixed state, in which only a portion of the axon membrane is in the excited state, were investigated by the same method. The property of the weak variable inward membrane current which preceded the appearance of discrete inward surges was investigated.