NEUROPEPTIDE ADAPTATION ASSOCIATED WITH OPIATE TOLERANCE

阿片类药物耐受的潜在机制(S)仍有待阐明。虽然对这种现象有几种理论假设，但最近内源性抗阿片肽(AOPS)，如神经肽FF(NPFF)的发现表明，内源性模型参与解释阿片类药物耐受的发展。NPFF是一种哺乳动物八肽，已被证明可以减弱阿片类药物诱导的各种作用，如抗伤害性和吗啡耐受和依赖的形成。有人建议，吗啡的给药释放抗阿片类药物，作为体内平衡机制的一部分。随着吗啡用量的增加，越来越多的抗阿片剂被释放到脑脊液中。作为直接后果，MU阿片受体(MOR)复合体下调，需要更大剂量的吗啡来克服内源性抗阿片剂的拮抗作用，从而产生越来越高程度的激动剂亚敏感性(耐受性)。本项目将探讨NPF减轻吗啡耐受的机制(S)。慢性(13天)脑室注射硫酸吗啡，通过阿尔赛特2001渗透压迷你泵，使大鼠耐受。由于先前的研究结果表明，慢性侧脑室注射吗啡和NPFF单独能够下调吗啡浓度，因此本提案是进一步研究NPFF减轻脊髓和与阿片类药物耐受相关的不同脑区(纹状体、大脑皮层和丘脑)吗啡耐受机制的极佳模型(S)。为了验证这一假设，将进行研究，以检查NPFF的慢性影响，以改变与吗啡耐受相关的MOR受体密度和信使RNA水平。其他实验将测试NPF对吗啡耐受性的慢性影响，通过MU介导的MOR信号转导通路的反应(cAMP水平和GTP-γ-S活性)来衡量。这些发现有望通过更清楚地了解在MOR系统中复杂的生化事件级联中发生相互作用的位置来描述NPF减弱吗啡耐受性的机制(S)。

The underlying mechanism(s) of opiate tolerance remains to be elucidated. Although several theories have been postulated for such phenomenon, recent findings of endogenous anti-opiate peptides (AOPs), like neuropeptide FF (NPFF), suggest the involve of an endogenous model to explain the development of opioid tolerance. NPFF is a mammalian octapeptide, that has been shown to attenuate various opiate- induced effects, like anti-nociception and the development of morphine tolerance and dependence. It is proposed that the administration of morphine releases anti-opiates as part of a homeostatic mechanism. As greater quantities of morphine are administered, increasing quantities of anti-opiates are released into the CSF. As a direct consequences mu opioid receptor (MOR) complex is down-regulated, and larger doses of morphine are required to overcome the antagonism by endogenous anti- opiates, producing progressively higher degrees of agonist sub-sensitivity (tolerance). The present project will examine the mechanism(s) by which NPFF attenuate morphine-induced tolerance. Rats will be made tolerant by chronic (13 days) intraventricular infusion of morphine sulfate, via the Alzet 2001 osmotic mini-pumps. Because previous findings have shown that chronic i.c.v infusion of morphine and NPFF alone were able to down-regulate MOR density, the present proposal represents an excellent model to further examine the mechanism(s) by which NPFF attenuates morphine tolerance in spinal cord and discrete brain regions (Striatum, Cerebral Cortex, and Thalamus) that are associated with opiate tolerance. To test this hypothesis, studies will be conducted to examine the chronic effects of NPFF to alter the MOR receptor density and messenger RNA level associated with morphine tolerance. Additional experiments will test the chronic effects of NPFF on morphine tolerance as measured by mu mediated responses of the MOR signaling transduction pathway (cAMP levels and GTP-gamma-S activity). These finding are expected to delineate the mechanism(s) by which NPFF attenuates morphine tolerance by providing a clearer understanding as to where the interaction is occurring within the complex cascade of biochemical events of the MOR system.