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Author Notes:

Correspondence: P.M. Iuvone, Dept. of Pharmacology, Emory University School of Medicine, 1510 Clifton Rd. NE, Atlanta, GA 30322 USA; Email: miuvone@pharm.emory.edu

Acknowledgments: The authors gratefully acknowledge the assistance of Dr. Nikita Pozdeyev, Dr. Rashidul Haque, and Ms. Jane Abbey.

Subjects:

Research Funding:

This work was supported by NIH grants EY014764 and EY004864.

Keywords:

  • photoreceptor
  • calcium
  • calcium channel
  • dopamine receptor
  • cAMP

Dopamine D4 receptors regulate intracellular calcium concentration in cultured chicken cone photoreceptor cells: relationship to dopamine receptor-mediated inhibition of cAMP formation

Tools:

Journal Title:

Brain Research

Volume:

Volume 1207

Publisher:

, Pages 111-119

Type of Work:

Article | Post-print: After Peer Review

Abstract:

Dopamine is a retinal neuromodulator secreted from amacrine and interplexiform cells. Activation of dopamine D4 receptors on photoreceptor cells reduces a light-sensitive pool of cAMP. The aim of present study was to evaluate the role of dopamine receptors and cAMP in the regulation of intracellular Ca2+ concentrations ([Ca2+]i) in photoreceptor cells of chick retina. Retinal cells from 6 day-old chicken embryos were isolated and cultured for 5–7 days prior to experiments. Cone photoreceptors were the predominant cell type in these cultures. Dopamine and agonists of dopamine D4 receptors suppressed K+-stimulated uptake of 45Ca2+ and [Ca2+]i, measured with the Ca2+-sensitive fluorescent dye fura-2 AM. The effects of the agonists were blocked by dopamine D2/D4 receptor antagonists or by pertussis toxin. 8Br-cAMP, a cell permeable analog of cAMP, had no effect on inhibition of K+-stimulated 45Ca2+ influx or [Ca2+]i by dopamine D2/D4 receptor agonists. Quinpirole inhibited the increase in cAMP level elicited by K+, which requires Ca2+ influx through voltage-gated Ca2+ channels, but not that induced by the calcium ionophore A23187. Moreover, dopamine had no effect on either forskolin-stimulated or Ca2+/calmodulin-stimulated adenylyl cyclase activity in cell membranes prepared from the cultured cells. These data indicate that the decrease of cAMP elicited by dopamine D4 receptor stimulation may be secondary to decreased [Ca2+]i.

Copyright information:

© 2008 Elsevier B.V. All rights reserved.

This is an Open Access work distributed under the terms of the Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported License (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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