Li Y, Kim J
Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912, USA.
Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912, USA.
Neuroscience. 2015 Dec 17;311:253-67. doi: 10.1016/j.neuroscience.2015.10.041. Epub 2015 Oct 26.
In the brain, CB1 cannabinoid receptors primarily mediate the effects of cannabinoids, but CB2 cannabinoid receptors (CB2Rs) have recently been discovered in the nervous system and also implicated in neuromodulatory roles. To understand the mechanisms of CB2R functions in the brain, it is essential to localize CB2Rs, but the types of cells expressing CB2Rs have been controversial. Unequivocal localization of CB2Rs in the brain has been impeded in part by the low expression levels of CB2Rs and poor specificity of detection methods. Here, we used an ultrasensitive and specific in situ hybridization method called the RNAscope to determine the spatial pattern of CB2R mRNA expression in the mouse hippocampus. CB2R mRNAs were mostly expressed in a subset of excitatory and inhibitory neurons in the CA1, CA3 and dentate gyrus areas, but rarely in microglia. CB2R knock-out mice were used as a negative control. Using the quantitative real-time polymerase chain reaction, we also found that the temporal pattern of CB2R mRNA expression was stable during postnatal development. Consistent with previous reports, the immunological detection of CB2Rs was not reliable, implying extremely low levels of the protein expression and/or insufficient specificity of the current anti-CB2R antibodies. Our findings of the expression patterns of CB2R mRNAs may help determine the cell types involved in, and hence the mechanisms of, the CB2R-mediated neuromodulation.
在大脑中，CB1大麻素受体主要介导大麻素的作用，但CB2大麻素受体（CB2Rs）最近在神经系统中被发现，并且也与神经调节作用有关。为了了解CB2R在大脑中的功能机制，定位CB2Rs至关重要，但表达CB2Rs的细胞类型一直存在争议。CB2Rs在大脑中的明确定位部分受到CB2Rs低表达水平和检测方法特异性差的阻碍。在这里，我们使用一种称为RNAscope的超灵敏且特异的原位杂交方法来确定小鼠海马体中CB2R mRNA表达的空间模式。CB2R mRNA主要在CA1、CA3和齿状回区域的一部分兴奋性和抑制性神经元中表达，但在小胶质细胞中很少表达。CB2R基因敲除小鼠用作阴性对照。使用定量实时聚合酶链反应，我们还发现CB2R mRNA表达的时间模式在出生后发育过程中是稳定的。与先前的报道一致，CB2Rs的免疫检测不可靠，这意味着蛋白质表达水平极低和/或当前抗CB2R抗体的特异性不足。我们关于CB2R mRNA表达模式的发现可能有助于确定参与CB2R介导的神经调节的细胞类型，从而确定其机制。
