kappa-opioid receptor expression defines a phenotypically distinct subpopulation of astroglia: relationship to Ca2+ mobilization, development, and the antiproliferative effect of opioids.
To assess the role of kappa-opioid receptors in astrocyte development, the effect of kappa-agonists on the growth of astroglia derived from 1-2-day-old mouse cerebra was examined in vitro. kappa-Opioid receptor expression was assessed immunocytochemically (using KA8 and KOR1 antibodies), as well as functionally by examining the effect of kappa-receptor activation on intracellular calcium ([Ca2+]i) homeostasis and DNA synthesis. On days 6-7, as many as 50% of the astrocytes displayed kappa-receptor (KA8) immunoreactivity or exhibited increases in [Ca2+]i in response to kappa-agonist treatment (U69,593 or U50,488H). Exposure to U69,593 (100 nM) for 72 h caused a significant reduction in number and proportion of glial fibrillary acidic protein-immunoreactive astrocytes incorporating bromodeoxyuridine (BrdU) that could be prevented by co-administering the kappa-antagonist, nor-binaltorphimine (300 nM). In contrast, on day 14, only 5 or 14%, respectively, of the astrocytes were kappa-opioid receptor (KA8) immunoreactive or displayed functional increases in [Ca2+]i. Furthermore, U69,593 (100 nM) treatment failed to inhibit BrdU incorporation at 9 days in vitro. Experimental manipulations showed that kappa-receptor activation increases astroglial [Ca2+]i both through influx via L-type channels and through mobilization of intracellular stores (which is an important Ca2+ signaling pathway in cell division). Collectively, these results indicate that a subpopulation of developing astrocytes express kappa-opioid receptors in vitro, and suggest that the activation of kappa-receptors mobilizes [Ca2+]i and inhibits cell proliferation. Moreover, the proportion of astrocytes expressing kappa-receptors was greatest during a period of rapid cell growth suggesting that they are preferentially expressed by proliferating astrocytes.
Gurwell
J A
JA
Department of Anatomy and Neurobiology, University of Kentucky Medical Center, Lexington, KY 40536-0084, USA.
Duncan
M J
MJ
Maderspach
K
K
Stiene-Martin
A
A
Elde
R P
RP
Hauser
K F
KF
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000737:chemistry* / Q000166:cytology; D044482:Benzeneacetamides; D001973:Bromodeoxyuridine; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured / Q000737:chemistry / Q000166:cytology / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D007150:Immunohistochemistry; D051379:Mice; D008813:Mice, Inbred ICR; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D009543:Nifedipine / Q000494:pharmacology; D010641:Phenotype; D011759:Pyrrolidines / Q000494:pharmacology; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000032:analysis / Q000235:genetics*; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors
D000700:Analgesics; D044482:Benzeneacetamides; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D009292:Narcotic Antagonists; D009294:Narcotics; D011759:Pyrrolidines; D017473:Receptors, Opioid, kappa; D009270:Naloxone; C051844:norbinaltorphimine; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D019284:Thapsigargin; D004247:DNA; D001973:Bromodeoxyuridine; D009543:Nifedipine; C045444:U 69593; D002118:Calcium