Abstract— The content of cyclic AMP and cyclic GMP was measured in whole eyes and in normal retinas from C57BL(6)J mice, in receptorless retinas from congenic mice homozygous for the receptor dystrophy gene (rd/rd), and in retinas from mice treated postnatally with monosodium glutamate. Normal retinas contain approx 320 μg of protein: dystrophic (rd/rd) retinas contain approx 110μg of protein, lack rods but possess some surviving cone somata and terminals: glutamate‐modified retinas contain approx 200 μg of protein and have both a reduced area and thickness with a marked deficiency of ganglion cells and amacrine cells. In normal mice, more than 90% of the cyclic GMP, but only 607, of the cyclic AMP of the whole eye was in the retina. In normal dark‐adapted retinas isolated under dim red light cyclic AMP and cyclic GMP content was 4.1 and 20.2pmol/retina, respectively. The content of both cyclic AMP and cyclic GMP was 40% less, 2.5 and 11.5pmol/retina, respectively, in light‐adapted retinas. In dark‐adapted retinas isolated under infra‐red light, cyclic AMP content was 40%, higher than that in retinas isolated under dim red light; cyclic GMP content was the same under these two conditions. Receptorless retinas contained approx 50% as much cyclic AMP and only 1‐2% as much cyclic GMP as normal retinas. Although glutamate‐modified retinas also had approx 50% as much cyclic AMP, they contained 60‐85%, as much cyclic GMP as normal retinas. Light decreased by 30‐50% levels of both cyclic AMP and cyclic GMP in glutamate‐modified retinas, but only reduced cyclic nucleotide levels in receptorless retinas by 20%. These data indicate that 95% or more of the cyclic GMP is in photoreceptor cells, whereas cyclic AMP is more evenly distributed throughout the retina. In addition, both cyclic AMP and cyclic GMP levels are influenced by light‐ and dark‐adaptation.

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