The Journal of Neuroscience, April 25, 2007, 27(17):4756-4764; doi:10.1523/JNEUROSCI.0183-07.2007
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Cellular/Molecular
Ambient Light Regulates Sodium Channel Activity to Dynamically Control Retinal Signaling
Tomomi Ichinose1 and
Peter D. Lukasiewicz1,2
Departments of 1Ophthalmology and Visual Sciences and 2Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110
Correspondence should be addressed to Peter D. Lukasiewicz, Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Campus Box 8096, 660 South Euclid Avenue, St. Louis, MO 63110. Email: lukasiewicz{at}vision.wustl.edu
The retinal network increases its sensitivity in low-light conditions to detect small visual inputs and decreases its sensitivity in bright-light conditions to prevent saturation. However, the cellular mechanisms that adjust visual signaling in the retinal network are not known. Here, we show that voltage-gated sodium channels in bipolar cells dynamically control retinal light sensitivity. In dim conditions, sodium channels amplified light-evoked synaptic responses mediated by cone pathways. Conversely, in bright conditions, sodium channels were inactivated by dopamine released from amacrine cells, and they did not amplify synaptic inputs, minimizing signal saturation. Our findings demonstrate that bipolar cell sodium channels mediate light adaptation by controlling retinal signaling gain.
Key words: patch clamp; sodium channel; ganglion cell; bipolar cell; dopamine; retinal network adaptation
Received Jan. 16, 2007;
revised March 20, 2007;
accepted March 28, 2007.
Correspondence should be addressed to Peter D. Lukasiewicz, Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Campus Box 8096, 660 South Euclid Avenue, St. Louis, MO 63110. Email: lukasiewicz{at}vision.wustl.edu
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