Cyclic GMP-sensitive conductance in outer segment membrane of catfish cones

Nature. 1985 Sep 5-11;317(6032):61-4. doi: 10.1038/317061a0.


A cyclic GMP-sensitive conductance has recently been observed with patch-clamp recording in excised inside-out patches of plasma membrane from frog and toad rod outer segments. This conductance has properties suggesting that it is probably the light-sensitive conductance involved in visual transduction. We now report a similar conductance in the outer segment membrane of catfish cones. Cyclic GMP showed positive cooperativity in opening this conductance, with a Hill coefficient of 1.6-3.0 and a half-saturating cGMP concentration of 35-70 microM. Cyclic AMP at 1 mM, or changing Ca concentration (in the presence of Mg), had little effect on the conductance. In physiological solutions the cGMP-induced current had a reversal potential near +10 mV; the current amplitude increased roughly exponentially with membrane potential in both depolarizing and hyperpolarizing directions. Our results suggest that cGMP is also the internal transmitter for phototransduction in cones.

Publication types

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

MeSH terms

  • Animals
  • Cell Membrane / physiology
  • Cyclic GMP / pharmacology
  • Cyclic GMP / physiology*
  • Electric Conductivity / drug effects
  • Fishes
  • Membrane Potentials
  • Photic Stimulation
  • Photoreceptor Cells / drug effects
  • Photoreceptor Cells / physiology*
  • Rod Cell Outer Segment / physiology*
  • Vision, Ocular*


  • Cyclic GMP