Mixed NOP/mu compounds and the involvement of their receptors in analgesia.

描述（由申请人提供）：孤啡肽/孤啡肽FQ是阿片肽家族中的肽，是NOP受体的内源性配体，广泛分布于脑中，参与大量生理过程。在涉及伤害性反应的脑区域、脊髓背角和背根神经节中的高表达水平强烈表明这是疼痛治疗的靶点。然而，在啮齿动物急性疼痛模型中，激动剂和拮抗剂似乎都不具有显著的抗伤害感受特性。基于NOP激动剂减弱由μ受体活化介导的奖赏和耐受性发展的能力，一种选择是使用混合的NOP/μ受体激动剂，而不是使用选择性NOP受体激动剂或拮抗剂。已证明此类化合物，如SR 14150，具有抗伤害感受活性而不诱导条件性位置偏爱。此外，最近的实验表明，NOP激动剂在慢性疼痛模型中具有抗异常性疼痛活性，并表明选择性NOP激动剂作为慢性疼痛而不是急性疼痛的治疗剂的潜力大得多。具体目标1中描述的实验将检验以下假设：NOP受体和/或N/OFQ在经历脊神经结扎（SNL）或糖尿病性神经病变的大鼠的选定脑区域、脊髓和DRG中上调，从而诱导慢性疼痛。这将通过定量rtPCR测量mRNA水平，通过Western分析测量蛋白质，通过测量SNL、糖尿病和对照大鼠脑区和脊髓中的[35 S]GTP S结合，以及通过测定i. c. v.和i.t.在SNL、糖尿病和对照大鼠中施用。具体目标2将确定NOP激动剂的作用是否是由于C纤维或A初级传入的选择性抑制。使用高或低的加热速率，C-或A -纤维可以独立地活化。此外，SNL和糖尿病性神经病变诱导这些传入神经的不同敏感性。将测定NOP激动剂阻断机械异常性疼痛、冷异常性疼痛和热痛觉过敏的能力，以更好地理解这些化合物减弱C-和A -纤维超敏性的能力，以及更好地理解NOP激动剂对不同慢性疼痛状态的潜在临床有用性。最后，将针对特定目标3合成新型丁丙诺啡类似物。这些化合物将被设计为具有比丁丙诺啡更高的NOP亲和力和活性，以降低成瘾倾向，从而改善丁丙诺啡作为镇痛剂和潜在的药物滥用药物的副作用特征。这些化合物以及其它混合的NOP/mu化合物将在体外表征结合亲和力和内在活性，并在体内表征抗伤害感受活性和滥用潜力。这些实验将大大提高对NOP活性化合物介导抗伤害感受性或抗异常性疼痛反应的机制的理解，并使选择性NOP激动剂和混合NOP/mu激动剂朝着临床用作具有降低的成瘾倾向的镇痛剂的方向发展。

DESCRIPTION (provided by applicant): Nociceptin/Orphanin FQ, the peptide in the opioid peptide family, and the endogenous ligand for the NOP receptor is widely distributed in the brain and involved in a large number of physiological processes. The high expression level in brain regions involved in nociceptive responses, the dorsal horn of the spinal cord, and dorsal root ganglion has strongly suggested this as a target for pain therapeutics. Nevertheless, neither agonists nor antagonists appear to have significant antinociceptive properties in rodent models of acute pain. Rather than using selective NOP receptor agonists or antagonists, one option would be to use a mixed NOP/mu receptor agonist, based upon the ability of NOP agonists to attenuate reward and tolerance development mediated by mu-receptor activation. Such compounds, such as SR14150, have been demonstrated to have antinociceptive activity without inducing a conditioned place preference. In addition, recent experiments have indicated that NOP agonists have anti-allodynic activity in chronic pain models and suggested a far greater potential for selective NOP agonists as a therapeutic for chronic rather than acute pain. The experiments described in Specific Aim 1 will test the hypothesis that NOP receptors and/or N/OFQ are upregulated in selected brain regions, spinal cord, and DRG of rats subjected to spinal nerve ligation (SNL) or diabetic neuropathy, inducing chronic pain. This will be examined by measuring mRNA level by quantitative rtPCR, and protein by Western analysis, by measuring [35S]GTP S binding in brain regions and spinal cord in SNL, diabetic, and control rats, and by determining the potency of NOP agonists for anti-allodynic activity after i.c.v. and i.t. administration in SNL, diabetic and control rats. Specific Aim 2 will determine whether the actions of NOP agonists are due to selective inhibition of C-fiber or A primary afferents. Using high or low heating rates C- or A -fibers can be independently activated. In addition, SNL and diabetic neuropathy induce differential sensitivity of these afferents. The ability of NOP agonists to block mechanical allodynia, cold allodynia, and thermal hyperalgesia will be determined to better understand both the ability of these compounds to attenuate the hypersensitivity of C- and A -fibers and also to better understand the potential clinical usefulness of NOP agonists for different chronic pain states. Finally, novel buprenorphine analogs will be synthesized for Specific Aim 3. These compounds will be designed to have higher NOP affinity and activity than buprenorphine to decrease the addiction liability and thus improve upon side effect profile of buprenorphine as an analgesic, and potentially as a drug abuse medication. These compounds, as well as other mixed NOP/mu compounds will be characterized in vitro for binding affinity and intrinsic activity, and in vivo for antinociceptive activity and abuse potential. These experiments will provide a greatly improved understanding of the mechanism by which NOP-active compounds mediate an antinociceptive or anti-allodynic response, and progress selective NOP agonists, and mixed NOP/mu agonists toward clinical use as analgesics with reduced addiction liability.