μ-opioid receptor down-regulation and cAMP-dependent protein kinase phosphorylation in a mouse model of chronic morphine tolerance
μ-opioid receptor down-regulation and cAMP-dependent protein kinase phosphorylation in a mouse model of chronic morphine tolerance
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DOI：
10.1016/s0169-328x(98)00005-9
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发表时间：
1998-04-01
期刊：
影响因子：
--
通讯作者：
Welch, SP
中科院分区：
文献类型：
--
作者：
Bernstein, MA;Welch, SP
放射性配体结合和转染受体的研究结果表明，μ受体下调和磷酸化可能是表达吗啡耐受的关键。在这项研究中，吗啡耐受的动物模型被用来关联与受体数量和磷酸化状态的变化的抗伤害感受。通过来自吗啡处理的小鼠的脑干组织的Western免疫测定来定量μ-阿片受体蛋白。使用受体的免疫沉淀（IP），然后进行反向磷酸化来评估受体磷酸化的程度。急性给药吗啡产生μ受体数量没有变化。慢性吗啡给药导致50%的受体蛋白质的数量比安慰剂治疗的样品减少。后磷酸化实验表明，下降cAMP依赖性蛋白激酶A（PKA）诱导的受体磷酸化后不久，急性吗啡给药，随后由纳洛酮可逆的增加与抗伤害感受的发病相关的受体的磷酸化。慢性吗啡给药导致PKA诱导的μ受体磷酸化减少。由于已经表明PKA活性在吗啡耐受小鼠的脑中增强，因此μ受体磷酸化的这种降低表明μ受体在吗啡耐受状态下可能在结构上或构象上发生改变。(C)1998年Elsevier Science B.V.
Results of radioligand binding and transfected receptor studies indicate that mu-receptor down-regulation and phosphorylation may be critical to the expression of morphine tolerance. In this study, an animal model of morphine tolerance was used to correlate antinociception with changes in receptor number and phosphorylation state. mu-Opioid receptor protein was quantitated by Western immunoassay of brainstem tissue from morphine-treated mice. Degree of receptor phosphorylation was assessed using immunoprecipitation (IP) of the receptor followed by back-phosphorylation. Acutely administered morphine produced no changes in mu-receptor quantity. Chronic morphine administration resulted in a 50% reduction in receptor protein quantity over placebo-treated samples. Back-phosphorylation experiments showed a drop in cAMP-dependent protein kinase A (PKA)-induced receptor phosphorylation shortly after acute morphine administration, followed by a naloxone-reversible increase in phosphorylation of the receptor that correlated with the onset of antinociception. Chronic morphine administration resulted in a decrease in PKA-induced phosphorylation of the mu-receptor. Since it has been shown that PKA activity is enhanced in the brains of morphine-tolerant mice, this decrease in mu-receptor phosphorylation suggests that the mu-receptor may be structurally or conformationally altered in the morphine-tolerant state. (C) 1998 Elsevier Science B.V.