Dark-adapted sensitivity, rhodopsin content, and background adaptation in pcd/pcd mice.

Adaptation to steady background lights has been investigated in pcd/pcd mice, a mutant strain with retinal degeneration. The hyperbolic stimulus/response functions of the scotopic b-wave of the electroretinogram show progressive changes. For the dark-adapted eyes the decrease in log sensitivity between ages 1 and 12 months is related linearly to the decreasing rhodopsin content. The observed decline in amplitude of maximum responses from dark-adapted eyes begins only after age 5 months and is accompanied by gradual prolongation of the time to the peak of half-maximum b-wave responses. At all ages, the sensitivity of response is changed little by increments of steady red background lights; the greatest slope of log sensitivity vs. log background plots is about +0.2. (In normal mice the slope is about +0.9.) The pcd/pcd b-wave results do not fit the normal empirical relation that is thought to reflect neural processing in the distal retina. Thus the present results suggest that neural processing is abnormal in pcd/pcd retinas.