dark current

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A current in the retina caused by constant influx of sodium ions through cGMP-gated sodium channels into the rod outer segment of retinal rods, and that is blocked by light (leading to hyperpolarization). The plasma membrane sodium channel is controlled through a cascade of amplification reactions initiated by photon capture by rhodopsin in the disc membrane. The so-called ‘dark current’ depolarizes the cell to around −40 mV.

Subjects: Medicine and Health.

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