Department of Biochemistry and Molecular Biology, Institute of Neuroscience, University of Salamanca, Salamanca, Spain.
Mol Pharmacol. 2010 Nov;78(5):935-42. doi: 10.1124/mol.110.066837. Epub 2010 Aug 17.
Morphine is one of the analgesics used most to treat chronic pain, although its long-term administration produces tolerance and dependence through neuronal plasticity. The ability of morphine to regulate neuron differentiation in vivo has been reported. However, the detailed mechanisms have not yet been elucidated because of the inability to separate maternal influences from embryonic events. Using zebrafish embryos as the model, we demonstrate that morphine decreases miR-133b expression, hence increasing the expression of its target, Pitx3, a transcription factor that activates tyrosine hydroxylase and dopamine transporter. Using a specific morpholino to knock down the zebrafish μ-opioid receptor (zfMOR) in the embryos and selective mitogen-activated protein kinase inhibitors, we demonstrate that the morphine-induced miR-133b decrease in zebrafish embryos is mediated by zfMOR activation of extracellular signal-regulated kinase 1/2. A parallel morphine-induced down-regulation of miR-133b was observed in the immature but not in mature rat hippocampal neurons. Our results indicate for the first time that zebrafish embryos express a functional μ-opioid receptor and that zebrafish serves as an excellent model to investigate the roles of microRNA in neuronal development affected by long-term morphine exposure.
吗啡是用于治疗慢性疼痛最常用的镇痛药之一，尽管其长期给药会通过神经元可塑性产生耐受性和依赖性。已经报道了吗啡在体内调节神经元分化的能力。然而，由于无法将母体影响与胚胎事件分开，因此详细的机制尚未阐明。使用斑马鱼胚胎作为模型，我们证明吗啡降低了 miR-133b 的表达，从而增加了其靶标 Pitx3 的表达，Pitx3 是一种激活酪氨酸羟化酶和多巴胺转运体的转录因子。使用特异性的 morpholino 在胚胎中敲低斑马鱼 μ-阿片受体 (zfMOR) 和选择性丝裂原活化蛋白激酶抑制剂，我们证明吗啡诱导的斑马鱼胚胎中 miR-133b 的减少是由 zfMOR 激活细胞外信号调节激酶 1/2 介导的。在不成熟但不是成熟的大鼠海马神经元中观察到与吗啡诱导的 miR-133b 下调平行。我们的研究结果首次表明，斑马鱼胚胎表达功能性 μ-阿片受体，并且斑马鱼是研究长期吗啡暴露影响神经元发育的 microRNA 作用的理想模型。
