Two types of cannabinoid receptor have been discovered so far, CB(1) (2.1: CBD:1:CB1:), cloned in 1990, and CB(2) (2.1:CBD:2:CB2:), cloned in 1993. Distinction between these receptors is based on differences in their predicted amino acid sequence, signaling mechanisms, tissue distribution, and sensitivity to certain potent agonists and antagonists that show marked selectivity for one or the other receptor type. Cannabinoid receptors CB(1) and CB(2) exhibit 48% amino acid sequence identity. Both receptor types are coupled through G proteins to adenylyl cyclase and mitogen-activated protein kinase. CB(1) receptors are also coupled through G proteins to several types of calcium and potassium channels. These receptors exist primarily on central and peripheral neurons, one of their functions being to inhibit neurotransmitter release. Indeed, endogenous CB(1) agonists probably serve as retrograde synaptic messengers. CB(2) receptors are present mainly on immune cells. Such cells also express CB(1) receptors, albeit to a lesser extent, with both receptor types exerting a broad spectrum of immune effects that includes modulation of cytokine release. Of several endogenous agonists for cannabinoid receptors identified thus far, the most notable are arachidonoylethanolamide, 2-arachidonoylglycerol, and 2-arachidonylglyceryl ether. It is unclear whether these eicosanoid molecules are the only, or primary, endogenous agonists. Hence, we consider it premature to rename cannabinoid receptors after an endogenous agonist as is recommended by the International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification. Although pharmacological evidence for the existence of additional types of cannabinoid receptor is emerging, other kinds of supporting evidence are still lacking.

中文翻译：

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国际药理学联合会。二十七。大麻素受体的分类。

到目前为止，已发现两种类型的大麻素受体：1990年克隆的CB（1）（2.1：CBD：1：CB1 :)和1993年克隆的CB（2）（2.1：CBD：2：CB2 :)。这些受体之间的区别基于其预测的氨基酸序列，信号传导机制，组织分布以及对某些有效激动剂和拮抗剂的敏感性的差异，这些激动剂和拮抗剂对一种或另一种受体类型表现出明显的选择性。大麻受体CB（1）和CB（2）具有48％的氨基酸序列同一性。两种受体类型均通过G蛋白偶联至腺苷酸环化酶和丝裂原激活的蛋白激酶。CB（1）受体还通过G蛋白偶联到几种类型的钙和钾通道。这些受体主要存在于中枢和外周神经元上，其功能之一是抑制神经递质的释放。确实，内源性CB（1）激动剂可能充当逆行突触信使。CB（2）受体主要存在于免疫细胞上。这类细胞也表达CB（1）受体，尽管程度较轻，但两种受体类型均具有广泛的免疫作用，包括调节细胞因子的释放。到目前为止，已发现的几种大麻素受体内源性激动剂中，最著名的是花生四烯酸乙醇酰胺，2-花生四烯酸甘油酯和2-花生四烯酸甘油醚。尚不清楚这些类花生酸分子是唯一的还是主要的内源性激动剂。因此，我们认为，根据国际药理学联合会命名法和药物分类委员会的建议，在内源性激动剂后重新命名大麻素受体为时尚早。