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Delta-opioid receptors on astroglial cells in primary culture: mobilization of intracellular free calcium via a pertussis sensitive G protein.

Journal article
Authors Thorleif Thorlin
Peter S Eriksson
Anders I. Persson
N David Åberg
Elisabeth Hansson
Lars Rönnbäck
Published in Neuropharmacology
Volume 37
Issue 3
Pages 299-311
ISSN 0028-3908
Publication year 1998
Published at Institute of Clinical Neurosciences
Institute of Clinical Neurosciences, Section of Neurological Diseases
Pages 299-311
Language en
Links www.ncbi.nlm.nih.gov/entrez/query.f...
Keywords Animals, Astrocytes, drug effects, metabolism, Calcium, metabolism, Calcium Channels, metabolism, Cells, Cultured, Cerebral Cortex, drug effects, metabolism, Enkephalin, D-Penicillamine (2,5)-, Enkephalins, pharmacology, GTP-Binding Proteins, antagonists & inhibitors, metabolism, Immunohistochemistry, Neuroglia, drug effects, metabolism, Neurons, drug effects, metabolism, Pertussis Toxin, Rats, Rats, Sprague-Dawley, Receptors, Opioid, delta, agonists, physiology, Virulence Factors, Bordetella, pharmacology
Subject categories Experimental brain research, Neurobiology

Abstract

Astrocytes in primary culture from rat cerebral cortex were probed concerning the expression of delta-opioid receptors and their coupling to changes in intracellular free calcium concentrations ([Ca2+]i). Fluo-3 or fura-2 based microspectrofluorometry was used for [Ca2+]i measurements on single astrocytes in a mixed astroglial-neuronal culture. Application of the selective delta-opioid receptor agonist, [D-Pen2, D-Pen5]-enkephalin (DPDPE), at concentrations ranging from 10 nM to 100 microM, induced concentration-dependent increases in [Ca2+]i (EC50 = 114 nM). The responses could be divided into two phases, with an initial spike in [Ca2+]i followed by either oscillations or a sustained elevation of [Ca2+]i. These effects were blocked by the selective delta-opioid receptor antagonist ICI 174864 (10 microM). The expression of delta-opioid receptors on astroglial cells was further verified immunohistochemically, using specific antibodies, and by Western blot analyses. Pre-treatment of the cells with pertussis toxin (100 ng/ml, 24 h) blocked the effects of delta-opioid receptor activation, consistent with a Gi- or Go-mediated response. The sustained elevation of [Ca2+]i was not observed in low extracellular Ca2+ and was partly blocked by nifedipine (1 microM), indicating the involvement of L-type Ca2+ channels. Stimulating neurons with DPDPE resulted in a decrease in [Ca2+]i, which may be consistent with the closure of the plasma membrane Ca2+ channels on these cells. The current results suggest a role for astrocytes in the response of the brain to delta-opioid peptides and that these opioid effects in part involve altered astrocytic intracellular Ca2+ homeostasis.

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