Dynamics of cyclic GMP synthesis in retinal rods

Neuron. 2002 Sep 26;36(1):81-91. doi: 10.1016/s0896-6273(02)00911-x.


In retinal rods, Ca(2+) exerts negative feedback control on cGMP synthesis by guanylate cyclase (GC). This feedback loop was disrupted in mouse rods lacking guanylate cyclase activating proteins GCAP1 and GCAP2 (GCAPs(-/-)). Comparison of the behavior of wild-type and GCAPs(-/-) rods allowed us to investigate the role of the feedback loop in normal rod function. We have found that regulation of GC is apparently the only Ca(2+) feedback loop operating during the single photon response. Analysis of the rods' light responses and cellular dark noise suggests that GC normally responds to light-driven changes in [Ca(2+)] rapidly and highly cooperatively. Rapid feedback to GC speeds the rod's temporal responsiveness and improves its signal-to-noise ratio by minimizing fluctuations in cGMP.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Artifacts
  • Calcium / metabolism
  • Calcium Signaling / physiology*
  • Calcium-Binding Proteins / deficiency*
  • Calcium-Binding Proteins / genetics
  • Cyclic GMP / biosynthesis*
  • Dark Adaptation / physiology
  • Feedback / physiology*
  • Guanylate Cyclase / metabolism*
  • Guanylate Cyclase-Activating Proteins
  • Hot Temperature
  • Membrane Potentials / physiology
  • Mice
  • Mice, Knockout
  • Photic Stimulation
  • Photons
  • Retinal Rod Photoreceptor Cells / cytology
  • Retinal Rod Photoreceptor Cells / metabolism*
  • Rhodopsin / metabolism
  • Vision, Ocular / physiology


  • Calcium-Binding Proteins
  • Guanylate Cyclase-Activating Proteins
  • Guca1a protein, mouse
  • Guca1b protein, mouse
  • Rhodopsin
  • Guanylate Cyclase
  • Cyclic GMP
  • Calcium