Xie W, Samoriski G M, McLaughlin J P, Romoser V A, Smrcka A, Hinkle P M, Bidlack J M, Gross R A, Jiang H, Wu D
Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642, USA.
Proc Natl Acad Sci U S A. 1999 Aug 31;96(18):10385-90. doi: 10.1073/pnas.96.18.10385.
Morphine and other micro opioids regulate a number of intracellular signaling pathways, including the one mediated by phospholipase C (PLC). By studying PLC beta3-deficient mice, we have established a strong link between PLC and mu opioid-mediated responses at both the behavioral and cellular levels. Mice lacking PLC beta3, when compared with the wild type, exhibited up to a 10-fold decrease in the ED(50) value for morphine in producing antinociception. The reduced ED(50) value was unlikely a result of changes in opioid receptor number or affinity because no differences were found in whole-brain B(max) and K(d) values for mu, kappa, and delta opioid receptors between wild-type and PLC beta3-null mice. We also found that opioid regulation of voltage-sensitive Ca(2+) channels in primary sensory neurons (dorsal root ganglion) was different between the two genotypes. Consistent with the behavioral findings, the specific mu agonist [D-Ala(2),(Me)Phe(4),Gly(ol)(5)]enkephalin (DAMGO) induced a greater whole-cell current reduction in a greater proportion of neurons isolated from the PLC beta3-null mice than from the wild type. In addition, reconstitution of recombinant PLC protein back into PLC beta3-deficient dorsal root ganglion neurons reduced DAMGO responses to those of wild-type neurons. In neurons of both genotypes, activation of protein kinase C with phorbol esters markedly reduced DAMGO-mediated Ca(2+) current reduction. These data demonstrate that PLC beta3 constitutes a significant pathway involved in negative modulation of mu opioid responses, perhaps via protein kinase C, and suggests the possibility that differences in opioid sensitivity among individuals could be, in part, because of genetic factors.
吗啡及其他微阿片类药物可调节多种细胞内信号通路，包括由磷脂酶C（PLC）介导的信号通路。通过研究PLCβ3基因敲除小鼠，我们在行为和细胞水平上都建立了PLC与μ阿片介导反应之间的紧密联系。与野生型小鼠相比，缺乏PLCβ3的小鼠在产生抗伤害感受作用时，吗啡的半数有效剂量（ED50）值降低了多达10倍。ED50值降低不太可能是阿片受体数量或亲和力变化的结果，因为在野生型和PLCβ3基因敲除小鼠之间，μ、κ和δ阿片受体的全脑Bmax和Kd值没有差异。我们还发现，两种基因型的初级感觉神经元（背根神经节）中电压敏感性钙通道的阿片调节存在差异。与行为学研究结果一致，特异性μ激动剂[D - Ala(2),(Me)Phe(4),Gly(ol)(5)]脑啡肽（DAMGO）在从PLCβ3基因敲除小鼠分离的神经元中比从野生型小鼠分离的神经元中，能在更大比例的神经元中诱导更大程度的全细胞电流降低。此外，将重组PLC蛋白重新导入PLCβ3缺陷的背根神经节神经元中，可使DAMGO反应降低至野生型神经元的水平。在两种基因型的神经元中，佛波酯激活蛋白激酶C均可显著降低DAMGO介导的钙电流降低。这些数据表明，PLCβ3构成了参与μ阿片反应负向调节的重要途径，可能是通过蛋白激酶C，这也提示个体间阿片敏感性差异可能部分归因于遗传因素。
