Cannabinoid subtype 2 receptors (CB₂Rs) are G protein‐coupled receptors (GPCRs) belonging to the endocannabinoid system, a complex network of signalling pathways leading to the regulation of key physiological processes. Interestingly, CB₂Rs are strongly up‐regulated in pathological conditions correlated with the onset of inflammatory events like cancer and neurodegenerative diseases. Therefore, CB₂Rs represent an important biological target for therapeutic as well as diagnostic purposes. No CB₂R‐selective drugs are yet on the market, thus underlining a that deeper comprehension of CB₂Rs’ complex activation pathways and their role in the regulation of diseases is needed. Herein, we report an overview of pharmacological and imaging tools such as fluorescent, positron emission tomography (PET), photochromic and covalent selective CB₂R ligands. These molecular probes can be used in vitro as well as in vivo to investigate and explore the unravelled role(s) of CB₂Rs, and they can help to design suitable CB₂R‐targeted drugs.

中文翻译：

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功能化大麻素亚型 2 受体配体：荧光、PET、光致变色和共价分子探针。

大麻素亚型 2 受体 (CB ₂ Rs) 是属于内源性大麻素系统的 G 蛋白偶联受体 (GPCR)，该系统是一个复杂的信号通路网络，可调节关键生理过程。有趣的是，CB ₂ Rs 在与癌症和神经退行性疾病等炎症事件发生相关的病理条件下强烈上调。因此，CB ₂ Rs代表了用于治疗和诊断目的的重要生物靶标。市场上尚未有 CB _{2 R 选择性药物，因此强调需要更深入地理解 CB 2} R 的复杂激活途径及其在疾病调节中的作用。在此，我们概述了药理学和成像工具，例如荧光、正电子发射断层扫描 (PET)、光致变色和共价选择性 CB ₂ R 配体。这些分子探针可用于体外和体内研究和探索 CB ₂ R的未阐明的作用，并且它们可以帮助设计合适的 CB ₂ R 靶向药物。