Key result
High cGMP inactivates cGMP-dependent conductance in rod outer segments by decreasing channel opening probability.
High concentrations of cGMP inactivate cGMP-dependent conductance in rod outer segment plasma membranes by decreasing channel opening probability.
Suggests concentration-dependent cGMP feedback in sensory channels; leaves open analogous effects in cardiac myocytes.
Integral cGMP-dependent currents as well as activity of single cGMP-activated channels in plasma membrane of rod outer segment (ROS) were recorded using the patch-clamp method. The dependence of integral currents on cGMP concentration is shown to be bell-shaped. Decrease in cGMP-dependent conductance at high cGMP concentration results from a decrease in channel opening probability. Thus, cGMP in high concentrations inactivates cGMP-dependent conductance.
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Zhainazarov et al. (1990) studied this question. cGMP was evaluated on cGMP-dependent conductance and channel opening probability. High concentrations of cGMP inactivated cGMP-dependent conductance in the plasma membrane of rod outer segments by decreasing channel opening probability.
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