The corneal ERG of the heterozygous retinal degeneration mouse

In the retina of the mouse heterozygous for retinal degeneration (+ rd) cGMP levels are reported to be considerably reduced from normal. The sensitivity and timing of the a- and b-wave components of the electroretinogram of anaesthetized, dark-adapted, heterozygous (+ rd) mice were measured and compared with those of normals (+ +). The (+ rd) mouse was found to be 0.43 log units more sensitive to flashes of green light than the normal for both a- and b-waves; the Vmax amplitude of the b-wave was larger; and variations in time-to-peak were of small magnitude except at low a-wave intensities, where the + rd responses were slowed compared with those of + +. Reduced phosphodiesterase activity has been suggested previously as a mechanism for altered cGMP levels in the rd mouse. The findings reported are interpreted in terms of reduced rates of cGMP metabolism.