[Light adaptation shift in the spectral sensitivity of cones in the frog Rana temporaria].

Spectral properties of frog's "red" cones and their mass receptor potential during blue colour adaptation (370--500 nm) have been investigated. The spectral sensitivity maximum depended on the season: in September, frogs had mean lambda max of 572 +/- 4, whereas in December and January-- 553 +/- 4 nm. Low background light resulted in shift of the spectral sensitivity curve to short wavelengths. The background effect did not depend on the wavelength. The shift of spectral sensitivity was accompanied by the increase of LRP to green stimuli and the decrease of LRP to shorter wavelengths. This effect developed not earlier than 5 min after the beginning of light adaptation. The range of the spectral sensitivity maximum shift varied within 575--525 nm, while changes in the amplitude did not exceed 25 nm. The data obtained indicate the shift of spectral sensitivity of "red" cones due to background illumination. This shift is presumably due to ionochromic changes of the visual pigment of the cones. It its turn, chloride redistribution might take place due to light-induced changes in the membrane potential of cells.