Discrete Threshold and Repetitive Responses 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

By using the so-called voltage-clamp technique, records were obtained indicating the presence of undulatory or oscillatory membrane current under fixed potential difference between the internal and external electrodes. This oscillatory membrane current was observed only when rectangular membrane depolarization was in the range between 15 and about 35 mv. The amplitude of the oscillatory membrane current was of the order of 1 ma/cm². The oscillatory membrane current disappeared suddenly when the depolarizing clamping pulse was reduced below the ‘threshold.’ Various sources of artefact were examined.