Ruzicka B B, Fox C A, Thompson R C, Meng F, Watson S J, Akil H
Mental Health Research Institute, University of Michigan, Ann Arbor 48109-0720, USA.
Brain Res Mol Brain Res. 1995 Dec 28;34(2):209-20. doi: 10.1016/0169-328x(95)00165-o.
The existence of opioid receptors within glial cell membranes has been proposed by several laboratories based on biochemical and radioligand binding data. The recent cloning of the mu, delta and kappa receptors has enabled us to directly examine the issue of opioid receptor expression in rat brain astroglia by using solution hybridization/ribonuclease protection assays to analyze the total RNA obtained from primary cultures of cortical, striatal, cerebellar, hippocampal and hypothalamic astrocytes. The results indicate that all five glial cultures expressed mu, delta and kappa receptor mRNA. The rank order of receptor mRNA abundance, expressed collectively across all five cultures, was determined to be delta > or = kappa >> mu. An analysis of the glial distribution profile for each receptor type revealed that mu receptor mRNA levels were the most abundantly expressed in cortical cultures, while the greatest levels of delta receptor mRNA were found in the cortical and hypothalamic cultures, and significant kappa receptor mRNA levels were produced by the cortical, hypothalamic and cerebellar cultures. Furthermore, the five glial cultures each expressed different levels of total opioid receptor (mu + delta + kappa) mRNA. The rank order of total opioid receptor mRNA expression across different astroglial cultures was found to be cortex > hypothalamus > cerebellum = hippocampus > striatum. An analysis of the relative expression profiles for mu, delta and kappa receptor mRNA within each culture revealed that all cultures manifested relatively high levels of delta and kappa receptor mRNA, but relatively low levels of mu receptor mRNA. Generally, cortical, hippocampal and hypothalamic cultures were characterized by comparable levels of delta and kappa receptor mRNA, and little, if any, mu receptor mRNA. However, striatal cultures were characterized by a high level of delta receptor mRNA which was approximately twice and four times that of the kappa and mu receptor mRNA, respectively. In contrast, cerebellar cultures expressed predominantly kappa receptor mRNA at a level which was almost twice that of the delta receptor mRNA, and expressed very little mu receptor mRNA. These data show that primary astroglial cultures not only express mu, delta and kappa receptor mRNAs, but they do so in a manner dependent upon receptor type and brain region. This suggests a regional heterogeneity of astrocytes with respect to opioid receptor expression, a characteristic previously described only for neurons. Furthermore, it suggests the existence of an additional anatomical component in CNS opioid systems.
几个实验室基于生化和放射性配体结合数据提出，胶质细胞膜内存在阿片受体。最近克隆出的μ、δ和κ受体，使我们能够通过溶液杂交/核糖核酸酶保护分析，直接检测大鼠脑星形胶质细胞中阿片受体的表达情况，该分析用于分析从皮质、纹状体、小脑、海马和下丘脑星形胶质细胞原代培养物中获取的总RNA。结果表明，所有五种胶质细胞培养物均表达μ、δ和κ受体mRNA。在所有五种培养物中共同表达的受体mRNA丰度的排序为δ≥κ>>μ。对每种受体类型的胶质细胞分布情况分析显示，μ受体mRNA水平在皮质培养物中表达最为丰富，而δ受体mRNA的最高水平见于皮质和下丘脑培养物，皮质、下丘脑和小脑培养物产生显著水平的κ受体mRNA。此外，五种胶质细胞培养物各自表达不同水平的总阿片受体（μ+δ+κ）mRNA。不同星形胶质细胞培养物中总阿片受体mRNA表达的排序为皮质>下丘脑>小脑=海马>纹状体。对每种培养物中μ、δ和κ受体mRNA的相对表达情况分析显示，所有培养物中δ和κ受体mRNA水平相对较高，但μ受体mRNA水平相对较低。一般来说，皮质、海马和下丘脑培养物的特征是δ和κ受体mRNA水平相当，几乎没有μ受体mRNA。然而，纹状体培养物的特征是δ受体mRNA水平较高，分别约为κ和μ受体mRNA的两倍和四倍。相比之下，小脑培养物主要表达κ受体mRNA，其水平几乎是δ受体mRNA的两倍，且μ受体mRNA表达极少。这些数据表明，原代星形胶质细胞培养物不仅表达μ、δ和κ受体mRNA，而且其表达方式取决于受体类型和脑区。这表明星形胶质细胞在阿片受体表达方面存在区域异质性，这一特征以前仅在神经元中描述过。此外，这表明中枢神经系统阿片系统中存在额外的解剖学成分。
