NEUROPEPTIDE ADAPTATION ASSOCIATED WITH OPIATE TOLERANCE

阿片类药物耐受的潜在机制仍有待阐明。虽然已有几种理论对这种现象进行了假设，但最近发现的内源性抗阿片肽（AOPs），如神经肽FF (NPFF)，表明涉及内源性模型来解释阿片耐受性的发展。NPFF是一种哺乳动物八肽，已被证明可以减弱阿片类药物引起的各种效应，如抗痛觉和吗啡耐受和依赖的发展。有人提出，吗啡的管理释放抗阿片类药物作为一个稳态机制的一部分。随着吗啡用量的增加，抗阿片类药物被释放到脑脊液中。其直接后果是阿片受体（MOR）复合物下调，需要更大剂量的吗啡来克服内源性抗阿片类药物的拮抗作用，逐渐产生更高程度的激动剂亚敏感性（耐受性）。本项目将研究NPFF减弱吗啡诱导的耐受性的机制。大鼠将通过Alzet 2001渗透微型泵在脑室内长期（13天）输注硫酸吗啡使其耐受。由于先前的研究结果表明，单独注射吗啡和NPFF能够下调MOR密度，因此本研究为进一步研究NPFF降低脊髓和与阿片类药物耐受性相关的脑分离区域（纹状体、大脑皮层和丘脑）吗啡耐受性的机制提供了一个很好的模型。为了验证这一假设，将进行研究，以检查NPFF对吗啡耐受相关的MOR受体密度和信使RNA水平的慢性影响。其他实验将通过MOR信号转导通路的mu介导反应（cAMP水平和gtp - γ - s活性）来检测NPFF对吗啡耐受性的慢性影响。这些发现有望通过更清晰地了解在MOR系统的复杂级联生化事件中相互作用发生的位置，来描述NPFF减弱吗啡耐受性的机制。

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.