CAMP CASCADE--ROLE IN OPIATE MODULATION OF NMDA CURRENTS

容忍和依赖是干扰人类社会发展的两大问题。 临床用途和阿片类药物，并促进其滥用。蜂窝手机 这两个过程背后的机制都没有得到很好的理解。 据报道，鸦片类药物会导致脑细胞活性发生显著变化 细胞内cAMP在大鼠脑内的级联，但尚不清楚这些是如何实现的 生化变化影响不同脑区的突触传递 区域以及它们是否在宽容的发展中发挥重要作用 和依赖。在海马齿状回，我们最近的研究 MU激动剂抑制NMDA受体介导的突触电流 颗粒细胞通过G蛋白介导的机制。目前的项目 建议进一步研究急性和慢性疾病的调节作用 阿片剂对齿状回NMDA电流的影响及cAMP的作用 传递阿片类药物效应的级联效应。要评估的假设是 急性阿片类药物通过抑制cAMP依赖抑制NMDA电流 颗粒细胞中的磷酸化，同时cAMP的上调级联 慢性阿片类药物可能会深刻地增强NMDA电流，进而 促进宽容和依赖的养成。为了测试这一点 假设、诱发和自发的NMDA电流将从 海马片齿状颗粒细胞的全细胞记录 技巧。实验将集中于以下具体目标：1) 确定突触类型(S)和位置(突触前与突触后) 抑制NMDA电流的阿片受体。2)研究NMDA如何 海流是通过操纵cAMP级联来调节的，如果是急性的 阿片类药物的作用是通过抑制cAMP级联反应来实现的。3)和4)至 评估慢性吗啡如何改变NMDA电流及其活性 CAMP在颗粒细胞中级联，如果这些变化有助于 宽容和依赖的发展。

Tolerance and dependence are two major problems which interfere with the clinical utility & opiate drugs and promote their abuse. The cellular mechanisms underlying either process have not been well understood. Opiates reportedly induce dramatic changes in the activity of intracellular cAMP cascade in rat brain, but it remains unclear how these biochemical changes affect synaptic transmission in different brain regions and if they play an important role in the development of tolerance and dependence. In hippocampal dentate gyrus, our recent studies have shown that mu agonists inhibit NMDA receptor-mediated synaptic currents in granule cells through a G protein-mediated mechanism. The present project proposes to further examine the modulatory effect of acute and chronic opiate on NMDA currents in the dentate, and to determine the role of cAMP cascade in transducing opiate effects. The hypothesis to be evaluated is that acute opiates suppress NMDA currents by inhibiting cAMP-dependent phosphorylation in granule cells, while the upregulation of cAMP cascade by chronic opiates may profoundly enhance NMDA currents, which in turn facilitates the development of tolerance and dependence. To test this hypothesis, evoked and spontaneous NMDA currents will be recorded from dentate granule cells in the hippocampal slice using whole-cell recording techniques. Experiments will focus on following specific aims: 1) To determine the type(s) and location (presynaptic vs. postsynaptic) of opiate receptors that inhibit NMDA currents. 2) To examine how NMDA currents are modulated by manipulation of the cAMP cascade, and if acute opioid effects are mediated by inhibiting cAMP cascade. 3) and 4) To evaluate how chronic morphine alters NMDA currents and the activity of cAMP cascade in granule cells, and if these alterations contribute to the development of tolerance and dependence.