ABSTRACT
Two general classes of light-evoked responses were recorded intracellularly from the retina of Strombus luhuanus. In one class, retinal illumination caused depolarization, the amplitude of which was graded with light intensity. In the other, it produced hyperpolarization and concomitant inhibition of repetitive action potentials.
There were two types of depolarizing waveform. Each was associated with a different type of intracellular recording site, characterized on the basis of electrical properties in the dark. In general, the type of response with a more rapid rate of decay was recorded from a site which exhibited a lower resting potential, higher input resistance, and longer ‘membrane charging time. ‘
The two depolarizing responses and the hyperpolarizing response apparently each arose from a different type of neurone. The depolarizing types, at least one of which is a photoreceptor, apparently give rise to the cornea-negativity of the electroretinogram and ‘on’ activity in the optic nerve fibres. The hyperpolarizing type apparently mediates ‘off’ activity in the optic nerve..
