The effects of barium on the suppression-recovery phenomenon in the aspartate isolated mass receptor response.

The relationship between the suppression-recovery phenomenon and sensitivity changes during light adaptation was investigated in the cone photoreceptors of the isolated, superfused bullfrog retina using barium as a tool. Barium reduced the shift of the stimulus-response function that occurs during light adaptation. Barium also reduced the maximum response amplitude seen after recovery from suppression induced by a flickering light stimulus. The effect of barium on the recovered response amplitude could not be explained by barium's known ability to attenuate the dark adapted cone response, since the magnitude of the depression of the recovered response amplitude was significantly greater at all concentrations than was the magnitude of the depression of the response of the dark adapted cones. Moreover, the thresholds for barium's effect, as well as the shapes of the dose-response curves, were quite different for the two types of responses. The results are consistent with the idea that the recovery from suppression induced by flicker is due to the same change in receptor sensitivity that manifests itself as a shift of the stimulus-response curve during light adaptation.