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Melatonin inhibits tetraethylammonium-sensitive potassium channels of rod ON type bipolar cells via MT2 receptors in rat retina.

Authors: Yang, XF  Miao, Y  Ping, Y  Wu, HJ  Yang, XL  Wang, Z 
Citation: Yang XF, etal., Neuroscience. 2011 Jan 26;173:19-29. doi: 10.1016/j.neuroscience.2010.11.028. Epub 2010 Nov 18.
Pubmed: (View Article at PubMed) PMID:21094224
DOI: Full-text: DOI:10.1016/j.neuroscience.2010.11.028

By challenging specific receptors, melatonin synthesized and released by photoreceptors regulates various physiological functions in the vertebrate retina. Here, we studied modulatory effects of melatonin on K+ currents of rod-dominant ON type bipolar cells (Rod-ON-BCs) in rat retinal slices by patch-clamp techniques. Double immunofluorescence experiments conducted in isolated cell and retinal section preparations showed that the melatonin MT(2) receptor was expressed in somata, dendrites and axon terminals of rat Rod-ON-BCs. Electrophysiologically, application of melatonin selectively inhibited the tetraethylammonium (TEA)-sensitive K+ current component, but did not show any effect on the 4-aminopyridine (4-AP)-sensitive component. Consistent with the immunocytochemical result, the melatonin effect was blocked by co-application of 4-phenyl-2-propionamidotetralin (4-P-PDOT), a specific MT(2) receptor antagonist. Neither protein kinase A (PKA) nor protein kinase G (PKG) seemed to be involved because both the PKA inhibitor Rp-cAMP and the PKG inhibitor KT5823 did not block the melatonin-induced suppression of the K+ currents. In contrast, application of the phospholipase C (PLC) inhibitor U73122 or the protein kinase C (PKC) inhibitor bisindolylmaleimide IV (Bis IV) eliminated the melatonin effect, and when the Ca(2)+ chelator BAPTA-containing pipette was used, melatonin failed to inhibit the K+ currents. These results suggest that suppression of the TEA-sensitive K+ current component via activation of MT(2) receptors expressed on rat Rod-ON-BCs may be mediated by a Ca(2)+-dependent PLC/inositol 1,4,5-trisphosphate (IP(3)/PKC signaling pathway.

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CRRD Object Information
CRRD ID: 9588677
Created: 2014-11-04
Species: All species
Last Modified: 2014-11-04
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.