Effects of animal age on the responses along the outer segment of retinal rod photoreceptors

THE aim of the present study was to determine whether the response gradient, known to exist along a rod outer segment, is influenced by age and developmental changes. Since intense light flashes saturate the responses of retinal rods and the time the response remains saturated increases from base to tip of the rod outer segment, one can use this difference in saturation times as a measure of the response gradient. During development and before sexual maturity (about one year postmetamorphosis) the differences between base and tip decreased, and this correlated with an acceleration of the light response in Xenopus laevis rods. The gradient along the rod outer segment then stabilized, while the response kinetics slowed and remained at a lower level. We conclude that photoreceptor responses and hence visual performance are affected by developmental changes.