title: Opiates selectively increase intracellular calcium in developing type-1 astrocytes: role of calcium in morphine-induced morphologic differentiation.
abstract: Endogenous opioids and opiate drugs inhibit nervous system maturation, in part, by affecting the growth of astrocytes. Opiates inhibit astrocyte proliferation and cause premature differentiation. The emerging importance of Ca2+ in astrocyte function prompted us to explore whether opiates might affect astrocyte development by altering Ca2+ homeostasis. Astrocyte-enriched cultures were derived from newborn ICR mouse cerebra. Quantitative fluorescent measurements of intracellular free Ca2+ ([Ca2+]i) using Fura-2 as well as fluo-3 and computer-aided image analysis showed that 1 microM morphine significantly increased [Ca2+]i in flat, polyhedral, glial fibrillary acidic protein (GFAP) immunoreactive astrocytes at 2 and 6 min, and at 72 h. Co-administration of 3 microM naloxone blocked morphine-dependent increases in [Ca2+]i. Treatment with 1 microM concentrations of the kappa-opioid receptor agonist, U69,593, but not equimolar amounts of mu ([D-Ala2,MePhe4,Gly(ol)5]enkephalin)- or delta ([D-Pen2,D-Pen5]enkephalin)-opioid receptor agonists, significantly increased [Ca2+]i in astrocytes. To assess the role of Ca2+ in morphine-induced astrocyte differentiation, untreated and 1 microM morphine-treated astrocyte cultures were incubated for 5 days in < 0.01, 0.3, 1.0, or 3.0 mM extracellular Ca2+ ([Ca2+]o), or incubated with 1.0 mM [Ca2+]o in the presence of 1 microM of the Ca2+ ionophore, A23187. The areas of single astrocytes were measured and there was a positive correlation between astrocyte area and [Ca2+]o. Morphine had an additive effect on area and form factor measures when [Ca2+]o was 1.0 mM. High [Ca2+]o (3.0 mM) alone mimicked the action of morphine. Morphine alone had no effect on astrocyte area in the presence of 3.0 mM Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Clinical Science, University of Kentucky Medical Center, Lexington 40536.
authors.forename: A
authors.initials: A
authors.lastname: Stiene-Martin
authors.forename: M P
authors.initials: MP
authors.lastname: Mattson
authors.forename: K F
authors.initials: KF
authors.lastname: Hauser
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000502:physiology; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D007091:Image Processing, Computer-Assisted; D051379:Mice; D008813:Mice, Inbred ICR; D009020:Morphine / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D009020:Morphine; D002118:Calcium