Regulation of gene expression mediated by the opioid receptor and the nociceptin receptor

本研究主要采用分子生物学、生物化学和电生理学方法分析了阿片类镇痛药和静脉麻醉药诱导的基因表达的变化，结果表明，将克隆的cDNA转染CHO细胞，激活阿片受体，诱导即早基因c-fos和junB的表达，这种诱导作用被百日咳毒素和PD 98059抑制，提示百日咳毒素敏感性G蛋白和丝裂原活化蛋白激酶（MAPK）参与了信号转导途径。这一机制可能与阿片耐受或依赖的分子机制有关，阿片类镇痛药的严重副作用，静脉麻醉药对神经细胞基因表达的影响尚未见报道。我们发现咪达唑仑诱导立即早期基因产物c-Fos和EGR-1的表达，这被PD 98059阻断。咪达唑仑以时间和剂量依赖性方式诱导MAPK活化。酪氨酸激酶和表皮生长因子受体抑制剂可阻断咪达唑仑诱导的MAPK激活。我们的研究结果可能表明静脉麻醉药通过改变基因表达模式而引起神经功能的长期变化。慢性激动剂暴露于表达μ-阿片受体的NG 108 -15细胞被证明可使阿片诱导的N型Ca^2+通道活性抑制脱敏。不同μ阿片受体选择性激动剂的脱敏程度不同，采用爪蟾卵母细胞表达系统检测挥发性麻醉剂对Ca^2+激活的K^+通道亚型的影响。结果表明，氟烷，异氟烷和七氟烷不影响SK亚型，但抑制IK亚型的活性。这一发现的生理意义仍有待阐明。

In this investigation, we mainly analyzed changes in gene expression induced by opioid analgesics and intravenous anesthetics, using molecular biological, biochemical and electrophysiological methods.Activation of the opioid receptor expressed by transfection of the cloned cDNA in CHO cells induced expression of immediate early genes, c-fos and junB.This induction was inhibited by pertussis toxin and PD98059, suggesting that pertussis toxin-sensitive G-proteins and mitogen- avtivated protein kinase (MAPK) are involved in the signal transduction pathway. This mechanism might be involved in the molecular mechanism of opioid tolerance or dependence, serious side effects of opioid analgesics.Effects of intravenous anesthetics on gene expression in neuronal cells have not been investigated. We found that midazolam induces expression of immediate early gene products, c-Fos and EGR-1, that was blocked by PD98059. Midazolam induced MAPK activation in a time- and dose-dependent manner. The midazolam-induced MAPK activation was blocked by inhibitors of tyrosine kinase and epidermal growth factor receptor. Our results may suggest that intravenous anesthetics induce long-term changes in neural functions by changes in gene expression patterns.Chronic agonist exposure of the NG108-15 cells transformed to express the μ-opioid receptor was demonstrated to cause desensitization of the opioid-induced inhibition of the the N-type Ca^<2+> channel activity. The magnitude of the desensitization was different among various μ-opioid receptor-selective agonists.Effects of volatile anesthetics on Ca^<2+>-activated K^+ channel subtypes were tested by the use of Xenopus oocyte expression system. It was demonstrated that halothane, isoflurane and sevoflurane do not affect the SK subtype, but suppressed the activity of the IK subtype. The physiological implication of this finding remains to be elucidated.