急、慢性吗啡依赖大鼠脑内Gi2蛋白的表达

目的研究吗啡依赖大鼠腹侧背盖区（VTA）、伏隔核（NAc）、前额皮质（PC）、海马及蓝斑（LC）各脑区Ⅱ型抑制性鸟苷酸结合蛋白（Gi2蛋白）的改变，探讨吗啡依赖的可能机制。方法36只SD大鼠随机分为6组，分别为急性吗啡依赖组、急性吗啡戒断组、急性空白对照组、慢性吗啡依赖组、慢性吗啡戒断组和慢性空白对照组。建立吗啡依赖大鼠模型。戒断组腹腔注射纳洛酮5mg／kg，作用30min。断头处死各组大鼠，取出脑组织，进行冰冻切片。用免疫组化技术检测NAc、PC、LC、VTA和海马的相对Gi2蛋白水平。结果急性吗啡依赖组和戒断组与急性空白对照组比较，NAc区Gi2蛋白水平明显降低（P〈0．01）。慢性吗啡依赖组和戒断组与慢性空白对照组比较，NAc区Gi2蛋白水平明显降低（P〈0．01），LC区Gi2蛋白水平明显升高（P〈0．01）。结论吗啡依赖可引起大鼠脑内Gi2蛋白水平发生改变，但各脑区Gi2蛋白水平的变化并不相同。Gi2蛋白水平改变可能是吗啡耐受和依赖潜在的分子机制。

Expression of Gi2 proteins in brain regions of acute or chronic morphine dependent rats

Objective To investigate the changes in inhibitory guanine nucleotide binding protein Gi_2 in five brain regions of morphine addicted rats: ventral tegmental area, nucleus accumbens, prefrontal cortex, hippocampus and locus caeruleus. Methods 36 adult male SD rats were randomly divided into six groups (n=6): acute morphine dependent group, acute abstinence group, acute control group, chronic morphine dependent group, chronic abstinent group and chronic control group. Morphine dependent models were reproduced. Withdrawal syndrome was induced with naloxone 5mg/kg for 30min in rats of abstinence group. All rats were sacrificed by decapitation. Frozen sections of coronal plane of respective brain regions (ventral tegmental area, nucleus accumbens, prefrontal cortex, locus coeruleus, hippocampus) were prepared. The relative concentrations of Gi_2 protein were determined with immunohistochemical methods. Results Gi_2 proteins in acute morphine dependent group and acute abstinence group were significantly decreased compared with that of acute control group in nucleus accumbens (P<0.01). Gi_2 proteins in chronic morphine dependent group and chronic abstinence group were significantly decreased in nucleus accumbens (P<0.01) and significantly increased in locus coeruleus (P<0.05) compared with that of chronic control group. Conclusion The morphine-induced changes in Gi_2 protein levels may reflect the changes in gene expression, and the degree of changes are different in different regions of the brain. Changes in Gi_2 proteins may affect signal transduction pathways in morphine dependent animals, and it might be the molecular mechanism of opioid tolerance and dependence.