Cyclic GMP increases photocurrent and light sensitivity of retinal cones

W. H. Cobbs, A. E. Barkdoll, Edward N Pugh Jr

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76 Scopus citations


Like retinal rods, cone photoreceptors contain cyclic GMP and light-activated phosphodiesterase1-3. The cGMP phosphodiesterase cascade is thought to mediate phototransduction in rods. Biochemical assays of nucleotide content in cone-dominant retinas, however, have failed to demonstrate light-induced changes in cGMP1. Changes in cyclic AMP following light exposure have been reported, leading to the suggestion that in cone phototransduction cAMP assumes a role analogous to that played by cGMP in rods4. Cyclic GMP introduced from tight-seal pipettes into isolated cones of the larval tiger salamander, Ambystoma tigrinum, rapidly increases light-modulated membrane current more than 10-fold. In cones, as in rods, cGMP also causes an approximately 10-fold increase in photocurrent duration and a 5- to 10-fold increase in light-sensitivity. Cyclic AMP has no effect on cone photocurrents under the same conditions. Because cGMP has similar effects on photocurrent magnitude and kinetics in both rods and cones, we conclude that cGMP plays corresponding roles in transduction in both vertebrate photoreceptor classes.

Original languageEnglish (US)
Pages (from-to)64-66
Number of pages3
Issue number6032
StatePublished - 1985
Externally publishedYes

ASJC Scopus subject areas

  • General


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