title: Modulation of agmatine on calcium signal in morphine-dependent CHO cells by activation of IRAS, a candidate for imidazoline I1 receptor.
abstract: The present study investigated the effects of agmatine action on imidazoline I1 receptor antisera-selected protein (IRAS), a candidate for imidazoline I1 receptor, on prolonged morphine-induced adaptations of calcium signal and long-lasting alterations in gene expression to further elucidate the role of IRAS in opioid dependence. Two cell lines, Chinese hamster ovary cells expressing mu opioid receptor alone (CHO-mu) and expressing mu opioid receptor and IRAS together (CHO-mu/IRAS), were used. After chronic treatment with morphine for 48 h, naloxone induced a significant elevation of intracellular calcium concentration ([Ca2+]i) in CHO-mu and CHO-mu/IRAS cells. Agmatine (0.01-3 microM) concentration-dependently inhibited the naloxone-precipitated [Ca2+]i elevation when co-pretreated with morphine in CHO-mu/IRAS, but not in CHO-mu. Efaroxan, an imidazoline I1 receptor-preferential antagonist, completely reversed the effect of agmatine in CHO-mu/IRAS. Agmatine (1-10 microM) administration after chronic morphine exposure for 48 h partially decreased the [Ca2+]i elevation in CHO-mu/IRAS which was entirely antagonized by efaroxan, but not in CHO-mu. In addition, agmatine (1 microM) co-pretreated with morphine attenuated the naloxone-precipitated increases of cAMP-responsive element binding protein and extracellular signal-regulated kinase 1/2 phosphorylations and c-Fos expression in CHO-mu/IRAS. These effects were blocked by efaroxan as well. Taken together, these results indicate that the agmatine-IRAS action system attenuates the up-regulations of Ca2+ signal and its downstream gene expression in morphine-dependent model in vitro, providing additional evidence to support the contribution of IRAS to opioid dependence.
authors.affiliation: Beijing Institute of Pharmacology and Toxicology, 27th Taiping Road, Beijing 100850, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Wu
authors.forename: Rui-Bin
authors.initials: RB
authors.lastname: Su
authors.forename: Yin
authors.initials: Y
authors.lastname: Liu
authors.forename: Xin-Qiang
authors.initials: XQ
authors.lastname: Lu
authors.forename: Jian-Quan
authors.initials: JQ
authors.lastname: Zheng
authors.forename: Bin
authors.initials: B
authors.lastname: Cong
authors.forename: Jin
authors.initials: J
authors.lastname: Li
mesh_terms: D000376:Agmatine / Q000494:pharmacology*; D000818:Animals; D016466:CHO Cells; D050882:CREB-Binding Protein / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D054755:Imidazoline Receptors; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009293:Opioid-Related Disorders / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011955:Receptors, Drug / Q000378:metabolism*
chemical_list: D054755:Imidazoline Receptors; D047908:Intracellular Signaling Peptides and Proteins; C458505:NISCH protein, human; D016760:Proto-Oncogene Proteins c-fos; D011955:Receptors, Drug; C410887:imidazoline I1 receptors; D009270:Naloxone; D000376:Agmatine; D009020:Morphine; D050882:CREB-Binding Protein; D048049:Extracellular Signal-Regulated MAP Kinases; D002118:Calcium