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The Journal of Neuroscience, July 21, 2004, 24(29):6621-6628; doi:10.1523/JNEUROSCI.1474-04.2004
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Cellular/Molecular
cGMP-Dependent Kinase Regulates Response Sensitivity of the Mouse On Bipolar Cell
Josefin Snellman1 and
Scott Nawy1,2
Departments of 1Neuroscience and 2Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, The Rose F. Kennedy Center, Bronx, New York 10461
The visual system can adjust its sensitivity over a wide range of light intensities. Photoreceptors account for some of this adjustment, but there is evidence that postreceptoral processes also exist. To investigate the latter, we pharmacologically mimicked the effects of light stimulation on mouse On bipolar cells, thus avoiding confounding effects of receptoral mechanisms. Here, we report that cGMP selectively enhances responses to dim, but not bright, stimuli through a purely postsynaptic mechanism. This action of cGMP was completely blocked by inhibitors of cGMP-dependent kinase. We propose that cGMP-dependent kinase decreases coupling of the On bipolar cell glutamate receptor to the downstream cascade, thus amplifying small decreases in photoreceptor transmitter levels that would otherwise go undetected by the visual system.
Key words: retina; On bipolar cell; G-protein-coupled receptor; cGK; mGluR6; PKG
Received April 19, 2004;
revised June 11, 2004;
accepted June 14, 2004.
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