Welch S P, Dunlow L D, Patrick G S, Razdan R K
Department of Pharmacology and Toxicology, Medical College of Virginia/Virginia Commonwealth University, Richmond, USA.
J Pharmacol Exp Ther. 1995 Jun;273(3):1235-44.
The antinociceptive effects of the putative endogenous cannabinoid ligand anandamide (ANA) and its fluorinated analog, fluoroanandamide (FA), were determined as measured by the tail-flick and p-phenylquinone (PPQ) stretch tests. The ED50 values (confidence limits) for ANA and FA were 77 (52-13) and 7 (2-21) micrograms/mouse, respectively, for the tail-flick test and 30 (23-41) and 0.5 (0.1-2) micrograms/mouse, respectively, for the PPQ test after intrathecal (i.t.) administration. ANA was not significantly less potent than delta 9-tetrahydrocannabinol (THC) in the tail-flick test, but it was less potent in the PPQ test. FA was more potent than either ANA or THC in tail-flick test. The antinociceptive effects of all drugs (administered i.t.) were blocked significantly or nearly abolished by the pretreatment of the mice with pertussis toxin (i.t.). Pretreatment of the mice with 5 and 25 micrograms forskolin per mouse or 10 micrograms 8-(4-chlorophenyl-thio)-adenosine-3',5'-monophosphate cyclic monosodium salt per mouse (both i.t.) significantly attenuated the antinociception produced by THC but not by ANA or FA. Various calcium modulators were tested in combination with THC, ANA, and FA, but they failed to alter the antinociceptive effects of the drugs. Various potassium channel blockers were tested in combination with the drugs. Apamin, a blocker of small (low)-conductance calcium-gated potassium channels that attenuates THC-induced antinociception, failed to alter ANA- or FA-induced antinociception. In contrast to THC, which is blocked by the kappa antagonist nor-binaltorphimine, ANA- and FA-induced antinociception was not altered by classic opioid antagonists. Also in contrast to THC, which enhances mu and delta opioid-induced antinociceptive effects, ANA failed to significantly alter opioid antinociception. ANA significantly shifted the THC dose-effect curve to the right. Thus, ED50 for DMSO/THC in the tail-flick test was shifted from 14 (7-29) to 54 (38-77) micrograms/mouse and was shifted in the hot-plate test from 22 (12-42) to 63 (43-92) micrograms/mouse. The magnitude of the shift in the ED50 was 3.8-fold in the tail-flick test and 2.9-fold in the hot-plate test. The shifts were parallel and significant. The Ki for the displacement of 3H-CP 55,940 binding by ANA and FA was 214 nM (+/- 45 S.E.M.) and 72 nM (+/- 5 S.E.M.), respectively, in pure spinal cord synaptosomes from the rat. ANA and FA were significantly cross-tolerant to THC. Although similarities between ANA and cannabinoids were shown, several marked differences were observed between ANA and the classic cannabinoids. ANA appears to function as both a cannabimimetic and a blocker of cannabinoid-induced antinociception.
通过甩尾试验和对苯二酚（PPQ）伸展试验测定了内源性大麻素配体花生四烯乙醇胺（ANA）及其氟化类似物氟花生四烯乙醇胺（FA）的抗伤害感受作用。鞘内注射后，在甩尾试验中，ANA和FA的半数有效剂量（ED50值，置信限）分别为77（52 - 13）和7（2 - 21）微克/小鼠；在PPQ试验中，分别为30（23 - 41）和0.5（0.1 - 2）微克/小鼠。在甩尾试验中ANA的效力不比Δ9 - 四氢大麻酚（THC）显著低，但在PPQ试验中效力较低。在甩尾试验中，FA比ANA或THC的效力更强。所有药物（鞘内注射）的抗伤害感受作用在给小鼠预先注射百日咳毒素（鞘内注射）后均被显著阻断或几乎消除。每只小鼠分别预先注射5微克和25微克福斯可林或10微克8 - （4 - 氯苯基硫代） - 腺苷 - 3',5' - 环一磷酸单钠盐（均为鞘内注射），可显著减弱THC产生的抗伤害感受，但对ANA或FA无此作用。将各种钙调节剂与THC、ANA和FA联合测试，但它们未能改变这些药物的抗伤害感受作用。将各种钾通道阻滞剂与这些药物联合测试。蜂毒明肽是小（低）电导钙门控钾通道的阻滞剂，可减弱THC诱导的抗伤害感受，但未能改变ANA或FA诱导的抗伤害感受。与被κ拮抗剂nor - 纳洛酮阻断的THC不同，经典阿片类拮抗剂未改变ANA和FA诱导的抗伤害感受。同样与增强μ和δ阿片类诱导的抗伤害感受作用的THC不同，ANA未能显著改变阿片类抗伤害感受。ANA使THC剂量 - 效应曲线显著右移。因此，在甩尾试验中，二甲基亚砜/THC的ED50从14（7 - 29）微克/小鼠移至54（38 - 皮77）微克/小鼠，在热板试验中从22（12 - 42）微克/小鼠移至63（43 - 92）微克/小鼠。在甩尾试验中ED50的移动幅度为3.8倍，在热板试验中为2.9倍。这些移动是平行且显著的。在大鼠纯脊髓突触体中，ANA和FA对3H - CP 55,940结合的置换解离常数（Ki）分别为214 nM（±45 S.E.M.）和72 nM（±5 S.E.M.））。ANA和FA对THC有显著的交叉耐受性。尽管显示出ANA与大麻素之间存在相似性，但在ANA与经典大麻素之间也观察到了一些显著差异。ANA似乎既起拟大麻作用，又起大麻素诱导的抗伤害感受的阻滞剂作用。
