Inhibitory Effect of Somatostatin-14 on L-Type Voltage-Gated Calcium Channels in Cultured Cone Photoreceptors Requires Intracellular Calcium

Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas Submitted 20 April 2009; accepted in final form 10 July 2009 Abstract The inhibitory effects of somatostatin have been well documented for many p...

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Published in:Journal of neurophysiology 2009-09, Vol.102 (3), p.1801-1810
Main Authors: Jian, Kuihuan, Barhoumi, Rola, Ko, Michael L, Ko, Gladys Y.-P
Format: Article
Language:English
Subjects:
Animals
Calcium - metabolism
Calcium Channels, L-Type - metabolism
Cells, Cultured
Chelating Agents - pharmacology
Chick Embryo
Circadian Rhythm - physiology
Cyanamide - metabolism
Drug Interactions
Egtazic Acid - analogs & derivatives
Egtazic Acid - pharmacology
Enzyme Inhibitors - pharmacology
Gene Expression Regulation - drug effects
Hormone Antagonists - pharmacology
Hormones - pharmacology
Intracellular Fluid - drug effects
Intracellular Fluid - metabolism
Membrane Potentials - drug effects
Membrane Potentials - physiology
Patch-Clamp Techniques - methods
Peptides, Cyclic - pharmacology
Pertussis Toxin - pharmacology
Retinal Cone Photoreceptor Cells - cytology
Retinal Cone Photoreceptor Cells - drug effects
Retinal Cone Photoreceptor Cells - physiology
Somatostatin - pharmacology
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Summary:Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas Submitted 20 April 2009; accepted in final form 10 July 2009 Abstract The inhibitory effects of somatostatin have been well documented for many physiological processes. The action of somatostatin is through G-protein-coupled receptor-mediated second-messenger signaling, which in turn affects other downstream targets including ion channels. In the retina, somatostatin is released from a specific class of amacrine cells. Here we report that there was a circadian phase-dependent effect of somatostatin-14 (SS14) on the L-type voltage-gated calcium channels (L-VGCCs) in cultured chicken cone photoreceptors, and our study reveals that this process is dependent on intracellular calcium stores. Application of 500 nM SS14 for 2 h caused a decrease in L-VGCC currents only during the subjective night but not the subjective day. We then explored the cellular mechanisms underlying the circadian phase-dependent effect of SS14. The inhibitory effect of SS14 on L-VGCCs was mediated through the pertussis-toxin-sensitive G-protein-dependent somatostatin receptor 2 (sst2). Activation of sst2 by SS14 further activated downstream signaling involving phospholipase C and intracellular calcium stores. Mobilization of intracellular Ca 2+ was required for somatostatin induced inhibition of photoreceptor L-VGCCs, suggesting that somatostatin plays an important role in the modulation of photoreceptor physiology. Address for reprint requests and other correspondence: G. Ko, Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, 4458 TAMU, College Station, TX 77843-4458, (E-mail: gko{at}cvm.tamu.edu )
ISSN:0022-3077
1522-1598
DOI:10.1152/jn.00354.2009