Agonist-Dependent Signaling and Post-Signaling Events of DOR

吗啡耐受的分子机制尚未完全确定。的当前模型 通过β-Arrestin途径的β-阿片受体（莫尔）脱敏不能解释许多 观察到其他神经递质受体活动，如NMDA，可能有助于吗啡 宽容其他阿片受体的活性，如6-阿片受体（DOR），可能涉及 吗啡耐受性的发展。由于吗啡可激活和脱敏DOR， 治疗，我们的工作假设是，后信号传导事件发生在DOR- 吗啡处理期间的神经元有助于耐受性的发展。我们的工作假设也是， 吗啡具有不同于其它阿片样物质激动剂的后信号传导事件。为了证明 根据这些假设，将建立吗啡激活DOR的激动剂依赖性信号传导事件。在 我们对莫尔信号传导的研究表明，吗啡与其他激动剂的不同之处在于其 激活ERK 1/2的途径。激动剂如埃托啡通过B-抑制蛋白依赖性激活ERK 1/2 途径，而吗啡通过PKC依赖性途径激活ERK 1/2。这种发散性激活导致 在活化的ERK 1/2和产生的转录本的差异易位中。因此， 在表达DOR的细胞模型中，将建立吗啡的后信号传导通路和后信号传导事件。的 PKC依赖性通路可能参与吗啡介导的DOR对ERK 1/2的激活， 被研究。将定义涉及的具体PKC亚型。之间的差异的原因 激动剂在选择途径中的作用将通过使用一种新的 蛋白酶测定系统将使用原代神经元培养物进行平行研究。封锁 DOR表达神经元中的特定PKC亚型对体内吗啡耐受性发展的影响将是 探讨了通过选择性地使吗啡信号通路失活， DOR神经元事件，可能阻断吗啡耐受而不改变吗啡 在含有莫尔的神经元中可以完成活动。

The molecular mechanism for morphine tolerance has not been firmly established yet. The current model of [j-opioid receptor (MOR) desensitization via the &-Arrestin pathway cannot account for the numerous observations that other neurotransmitter receptor activities, such as NMDA, could contribute to morphine tolerance. The activity of other opioid receptors, such as the 6-opioid receptor (DOR), could be implicated in morphine tolerance development also. Since morphine can activate and desensitize DOR during prolonged treatment, our working hypothesis is that the post-signaling events occurring within the DOR-containing neurons during morphine treatment contribute to tolerance development. Our working hypothesis also is that morphine has post-signaling events distinct from those of other opioid agonists. In order to demonstrate these hypotheses, agonist-dependent signaling events will be established for morphine activation of DOR. In our studies with MOR signaling, we have demonstrated that morphine differs from other agonists in its pathway to activate ERK1/2. Agonists such as etorphine activate ERK1/2 via the B-Arrestin-dependent pathway, while morphine activates ERK1/2 via the PKC-dependent pathway. This divergent activation results in differential translocation of the activated ERK1/2 and the transcripts produced. Therefore, the signaling pathway and the post-signaling events of morphine in cell models expressing DOR will be established. The possible involvement of the PKC-dependent pathway on morphine-mediated DOR activation of ERK1/2 will be studied. The specific PKC subtypes involved will be defined. The reasons for the differences among agonists in selecting a pathway will be investigated by monitoring protein-protein interactions using a novel protease assay system. Parallel studies will be conducted with primary neuronal cultures. The blockade of specific PKC subtypes in DOR-expressing neurons on in vivo morphine tolerance development will be explored. By selectively inactivating the morphine signaling pathway, and subsequently its post-signaling events in DOR-containing neurons, possible blockade of morphine tolerance without altering morphine activities in MOR containing neuron could be accomplished.