The Circadian Clock in the Retina Controls Rod-Cone Coupling

Sep 13, 2008Neuron

The eye's internal clock controls communication between rod and cone cells

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Abstract

Rod-cone coupling is remarkably robust at night but weak during the day.

Rod and cone photoreceptor cells in the retina are connected by gap junctions.
The retinal circadian clock regulates the strength of rod-cone coupling.
Dopamine D(2)-like receptors are activated during the day, leading to weaker coupling.
At night, the coupling strength increases, allowing cones to detect dim light signals from rods.
This synaptic switch may enhance the ability to detect large dim objects during nighttime.

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Although rod and cone photoreceptor cells in the vertebrate retina are anatomically connected or coupled by gap junctions, a type of electrical synapse, rod-cone electrical coupling is thought to be weak. Using tracer labeling and electrical recording in the goldfish retina and tracer labeling in the mouse retina, we show that the retinal circadian clock, and not the retinal response to the visual environment, controls the extent and strength of rod-cone coupling by activating dopamine D(2)-like receptors in the day, so that rod-cone coupling is weak during the day but remarkably robust at night. The results demonstrate that circadian control of rod-cone electrical coupling serves as a synaptic switch that allows cones to receive very dim light signals from rods at night, but not in the day. The increase in the strength and extent of rod-cone coupling at night may facilitate the detection of large dim objects.

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The Circadian Clock in the Retina Controls Rod-Cone Coupling

Abstract

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