Spectral sensitivity of L-TypeS-Potentials in a teleost retina

Abstract

A review is presented of studies on spectral sensitivity of hyperpolarizing ( L-type) S-potentials, which shows the existence, in Eugerres plumieri, of three spectral sensitivity curves in light adaptation, corresponding to the three cone photopigments; in dark adaptation, a fourth spectral sensitivity was found with maximum corresponding to rhodopsin absorption. It is now shown that cells with the latter spectral sensitivity shift their maximum upon exposure to a background light, that this spectral sensitivity shift is progressive and reversible, and that it can be produced whether the adapting light falls on the same, or on a different receptor population as that tested, indicating that it is not an exclusively photochemical event, but some neural mechanism must mediate such a shift. The involvement of S-potential producing cells in these adaptive changes was explored by studying dark resting potentials and intensity-response relationships. Dark resting potentials before and after spectral sensitivity shifts, both in cells of different spectral sensitivities and in either adaptive state, do not differ significantly, indicating that adaptation is indpendent of S-unit resting potential. Intensity-response relationships are similar for the different type of S-potentials in either adaptive state, suggesting identical generating mechanisms for all of them.