Bioactivity Of Opioidmimetic Substances

研究人员在小鼠体内测定了最近开发的阿片样物质的镇痛活性，并与吗啡进行了比较，并使用特异性阿片受体拮抗剂来评估其作用方式。抗痛感谱与体外功能药理学数据（GPI，豚鼠回肠和MVD，小鼠输精管）相似，并反映了阿片受体的结合亲和力（参见项目1，有关化合物与-和-阿片受体相互作用的详细信息）。一系列新的含烷基和烷基吡嗪酮基团的类阿片化合物在体内具有优异的活性。特别是，其中一种在体外注射后的甩尾试验中产生的镇痛效果比吗啡强60到71倍；脊柱（甩尾试验）比椎骨上效应（热板试验）强2-3倍。特别是，化合物3-[4'- dmt -氨基丁基)-6-（3'- dmt -氨基丙基）-5-甲基-2（1H）吡嗪酮具有非常高的亲和力（Ki mu = 0.02 nM），选择性（δ /mu = 1520）和激动剂活性（GPI, IC50 = 1.7 nM），在所有检测系统中对δ受体的活性都很弱。该化合物主要通过mu-2受体亚型脊髓抗痛觉作用产生脊髓抗痛觉；然而，mu-1亚型在脊柱上占主导地位。sc注射产生中枢神经系统介导的抗痛觉作用，证明该化合物可以通过胃肠道上皮和调节血脑屏障（BBB）的毛细血管紧密连接的膜屏障。然而，每天注射一周后获得的耐受性与吗啡相当，这表明两种物质通过类似的机制作用于mu-阿片受体。

Summary of Work: The analgesic activity of recently developed opioidmimetic substances was determined in vivo in mice in comparison to morphine and using specific opiate-receptor antagonists to assess their mode of action. The antinociception profile paralleled that of the in vitro functional pharmacological data (GPI,guinea-pig ileum and MVD, mouse vas deferens), and reflected the opioid-receptor binding affinity (see, Project 1 for details on the interaction of compounds with delta- and mu-opioid receptors). A series of novel Dmt-containing alkyl and alkyl pyrazinone group as opioidmimetic compounds had exceptional activity in vivo. In particular, one of which was 60- to 71-fold more potent than morphine in generating analgesia by the tail-flick test after i.c.v. administration; the spinal (tail-flick test) is more potent than the supraspinal effects (hot-plate test) by a factor of 2-3. In particular, the compound 3-[4'-Dmt-aminobutyl)-6-(3'-Dmt-aminopropyl)-5-methyl-2(1H)pyrazinone had very high affinity (Ki mu = 0.02 nM), selectivity (delta/mu = 1,520) and agonist activity (GPI, IC50 = 1.7 nM) with weak activity toward the delta receptor in all assay systems. This compound acted to produce spinal antinociception primarily through spinal antinociception using the mu-2 receptor subtype; however, the mu-1 subtype dominates supraspinally. The s.c. injection produced CNS-mediated antinociception, providing evidence the compound passed through membrane barriers in both the gastrointestinal epithelium and in the microcapillary tight junctions that regulate the blood-brain barrier (BBB). However, a tolerance was obtained after a week of daily injections that was equivalent to morphine and suggests that both substances act through similar mechanisms at mu-opioid receptors. Another class of Dmt-containing pyrazinone compounds, the 3,6-bis-[Dmt-NH-(CH2)n]-2(1H)-pyrazinone compounds not only exhibited central (CNS) mediated analgesia, but also were orally bioavailable opioid mimetics. These symmetric substances displayed high affinity for mu-opioid receptors (Ki = 0.04-0.12 nM) and potent angonism on GPI (IC50 = 1.3-1.9 nM). They produced analgesia in vivo by i.c.v. administration that was 50- to 63-fold more potent than morphine, but only about half as potent when injected s.c. or administered orally, which is still orders of magnitude greater than other endogenous opioid peptides and, importantly, were unmodified by glycosylation, adamantane, triglycerides, halogens, antibody, biotin, bulky organic molecules, esterification of a C-terminal carboxyl group (of which none exist in these compounds) or O-acylation of the phenolic hydroxyal group of Tyr or Dmt, nor was it necessary to absorb them onto polysorbate coated nanoparticles to induced uptake through the BBB. Studies a group of mu opioid substances containing Dmt in lieu of Tyr in endomorphins-1 and -2 revealed differences in their mode of action that also serve to differential these stucturally related compounds. Whereas both compounds exhibited potent analgesia, their mode of action and degree of analgesia was significantly different. Dmt enhanced all measured parameters of activity by orders of magnitude both in vitro and in vivo.