期刊
BRAIN RESEARCH
卷 1207, 期 -, 页码 111-119出版社
ELSEVIER
DOI: 10.1016/j.brainres.2008.02.025
关键词
photoreceptor; calcium; calcium channel; dopamine receptor; cAMP
资金
- NEI NIH HHS [R01 EY004864-25, EY004864, P30 EY006360, R01 EY014764-04, R01 EY004864, EY014764, R01 EY014764] Funding Source: Medline
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 the 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 Ca-45(2+) and [Ca2+](i), measured with the Ca2+-sensitive fluorescent dye fura-2AM. 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 Ca-45(2+) 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). (C) 2008 Elsevier B.V. All rights reserved.
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