Felder C C, Joyce K E, Briley E M, Mansouri J, Mackie K, Blond O, Lai Y, Ma A L, Mitchell R L
Laboratory of Cell Biology, National Institute of Mental Health, Bethesda, Maryland 20892, USA.
Mol Pharmacol. 1995 Sep;48(3):443-50.
The recently cloned CB2 cannabinoid receptor subtype was stably transfected into AtT-20 and Chinese hamster ovary cells to compare the binding and signal transduction properties of this receptor with those of the CB1 receptor subtype. The binding of [3H]CP 55,940 to both CB1 and CB2 was of similar high affinity (2.6 and 3.7 nM, respectively) and saturable. In competitive binding experiments, (-)-delta 9-tetrahydrocannabinol and CP 55,940 were equipotent at the CB1 and CB2 receptors, but WIN 55212-2 and cannabinol bound with higher affinity to the CB2 than the CB1 receptor. HU 210 had a higher affinity for the CB1 receptor. Anandamide, a recently identified endogenous cannabinoid agonist, was essentially equipotent at both receptor subtypes. The structurally related fatty acid ethanolamides dihomo-gamma-linolenylethanolamide and mead ethanolamide also bound with relatively equal affinity to both receptors, but adrenylethanolamide had a higher affinity for the CB1 receptor. The rank order of potency and efficacy for binding of the selected agonists to the CB1 and CB2 receptors was mimicked in functional inhibition of cAMP accumulation experiments for all compounds tested. Both CB1 and CB2 receptors couple to the inhibition of cAMP accumulation that was pertussis toxin sensitive. SR141716A, a CB1 receptor antagonist, was a poor antagonist at the CB2 receptor in both binding and functional inhibition of cAMP accumulation experiments. When expressed in AtT-20 cells, the CB1 receptor mediated an inhibition of Q-type calcium channels and an activation of inward rectifying potassium channels. In contrast, the CB2 receptor did not modulate the activity of either channel under identical assay conditions. Similar to results obtained for CB1 receptor, the CB2 receptor did not couple to the activation of phospholipases A2, C, or D or to the mobilization of intracellular Ca2+. Except for its inability to couple to the modulation of Q-type calcium channels or inwardly rectifying potassium channels, the CB1 and CB2 receptors display similar pharmacological and biochemical properties.
最近克隆的CB2大麻素受体亚型被稳定转染到AtT-20细胞和中国仓鼠卵巢细胞中，以比较该受体与CB1受体亚型的结合和信号转导特性。[3H]CP 55,940与CB1和CB2的结合具有相似的高亲和力（分别为2.6和3.7 nM）且可饱和。在竞争性结合实验中，(-)-δ9-四氢大麻酚和CP 55,940在CB1和CB2受体上的效力相当，但WIN 55212-2和大麻酚与CB2受体的结合亲和力高于CB1受体。HU 210对CB1受体具有更高的亲和力。花生四烯酸乙醇胺，一种最近发现的内源性大麻素激动剂，在两种受体亚型上的效力基本相当。结构相关的脂肪酸乙醇酰胺二高-γ-亚麻酸乙醇酰胺和二十碳五烯酸乙醇酰胺与两种受体的结合亲和力也相对相等，但肾上腺素乙醇酰胺对CB1受体具有更高的亲和力。在所有测试化合物的cAMP积累实验的功能抑制中，所选激动剂与CB1和CB2受体结合的效力和效能的排名顺序被模拟。CB1和CB2受体均与百日咳毒素敏感的cAMP积累抑制偶联。CB1受体拮抗剂SR141716A在结合实验和cAMP积累实验的功能抑制中，对CB2受体的拮抗作用较弱。当在AtT-20细胞中表达时，CB1受体介导Q型钙通道的抑制和内向整流钾通道的激活。相反，在相同的测定条件下，CB2受体未调节任何一种通道的活性。与CB1受体获得的结果相似，CB2受体未与磷脂酶A2、C或D的激活或细胞内Ca2+的动员偶联。除了无法与Q型钙通道或内向整流钾通道调节偶联外，CB1和CB2受体表现出相似的药理和生化特性。
