Why does the administration of a drug that blocks phosphodiesterase (PDE) in retinal rod cells improve vision in individuals with certain forms of inherited retinal degeneration?

💡 Explanation

Blocking PDE increases cGMP levels, because PDE normally breaks down cGMP. Elevated cGMP leads to prolonged opening of cGMP-gated channels in rod cells, extending the signaling cascade and improving light detection. Therefore, vision improves, rather than being impaired by reduced signaling or unrelated processes.

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