Center for Drug Discovery (C.A.P., K.V., A.M.) and Department of Pharmaceutical Sciences (C.A.P., G.R.C., A.M.), Northeastern University, Boston, Massachusetts; and Preclinical Pharmacology Program, McLean Hospital, Belmont, Massachusetts (C.A.P., A.S.Z., J.B.)
Center for Drug Discovery (C.A.P., K.V., A.M.) and Department of Pharmaceutical Sciences (C.A.P., G.R.C., A.M.), Northeastern University, Boston, Massachusetts; and Preclinical Pharmacology Program, McLean Hospital, Belmont, Massachusetts (C.A.P., A.S.Z., J.B.).
J Pharmacol Exp Ther. 2018 Mar;364(3):485-493. doi: 10.1124/jpet.117.245647. Epub 2018 Jan 8.
AM6538 is a cannabinoid antagonist that binds CB1 receptors expressed in HEK-293 cells in a wash-resistant manner. The effects of AM6538 in live animals has not previously been established. We characterized the antagonist effects of AM6538 in male mice, using a warm-water tail-withdrawal assay, and in male squirrel monkeys trained to discriminate the CB1 agonist AM4054 from vehicle. The cannabinoid agonists WIN 55,212, Δ-tetrahydrocannabinol (THC), and AM4054 all produced 100% maximum possible antinociceptive effects in mice following vehicle pretreatment. One-hour pretreatment with increasing doses of AM6538 (0.1-10 mg/kg) produced first rightward, then downward shifts of the agonist dose-effect functions. Rimonabant, 1-10 mg/kg, produced parallel rightward shifts of the AM4054 dose-effect functions, and baseline effects of AM4054 were nearly recovered within 24 hours following 10 mg/kg of rimonabant. In contrast, in mice treated with 10 mg/kg of AM6538, antagonism of THC or AM4054 lasted up to 7 days. AM6538 also antagonized the discriminative stimulus effects of AM4054 in squirrel monkeys in a dose-related manner, and the effects of 3.2 mg/kg of AM6538 endured for more than 7 days. The effective reduction in CB1 receptor reserve was used to calculate the relative efficacy (tau values) of WIN 55,212, THC, and AM4054 in mice and of AM4054 monkeys, with results indicating that THC has a lower efficacy than WIN 55,212 or AM4054 in mice. These results demonstrate that AM6538 is a long-acting CB antagonist in vivo, and further suggest that differences in CB efficacy can be revealed in behavioral assays following AM6538 treatment.
AM6538 是一种大麻素拮抗剂，以可洗脱的方式结合在表达于 HEK-293 细胞的 CB1 受体上。AM6538 在活体动物中的作用以前尚未确定。我们使用温水尾巴回缩试验对雄性小鼠和经过训练以区分 CB1 激动剂 AM4054 与载体的雄性松鼠猴表征了 AM6538 的拮抗剂作用。在用载体预处理后，大麻素激动剂 WIN 55,212、Δ-四氢大麻酚 (THC) 和 AM4054 均在小鼠中产生了 100%的最大可能镇痛作用。用递增剂量的 AM6538（0.1-10 mg/kg）预处理 1 小时，会首先使激动剂剂量-效应函数发生右移，然后再向下移。1-10 mg/kg 的利莫那班产生 AM4054 剂量-效应函数的平行右移，并且在用 10 mg/kg 的利莫那班处理后 24 小时内，AM4054 的基线作用几乎完全恢复。相比之下，在用 10 mg/kg 的 AM6538 处理的小鼠中，THC 或 AM4054 的拮抗作用可持续长达 7 天。AM6538 还以剂量相关的方式拮抗 AM4054 在松鼠猴中的辨别刺激作用，并且 3.2 mg/kg 的 AM6538 的作用持续了超过 7 天。有效减少 CB1 受体储备用于计算 WIN 55,212、THC 和 AM4054 在小鼠中的相对效力（tau 值）和 AM4054 在猴子中的相对效力，结果表明，在小鼠中，THC 的效力低于 WIN 55,212 或 AM4054。这些结果表明，AM6538 是一种体内长效 CB 拮抗剂，并且进一步表明，在 AM6538 处理后的行为测定中，可以揭示 CB 效力的差异。
