RECEPTOR CURRENT OSCILLATIONS EVOKED BY LOCAL ILLUMINATION IN LIMULUSVENTRAL NERVE PHOTORECEPTORS

Light flashes to spots on ventral photoreceptors induced complex curre nt bursts or oscillations. The number of peaks in a burst was not corr elated with the number of effective photons. Intervals between peaks w ere constant in each cell. Net charge fluxes during bursts were larger than the charge flux during a single bump multiplied by the number of peaks. The number of peaks, current-time-integrals, and kinetics of b ursts evoked either by light spots or by illumination of the same enti re cell were similar. Occasionally, bursts appeared at stimulus intens ities corresponding with only 1-2 effective photons. At higher intensi ties they occurred more frequently, and the average burst-evoking inte nsity corresponded with 6 effective photons. We conclude that a single photoisomerization can induce a current burst due to a local oscillat ory process.