Morphine induced alterations in NMDA receptor subunit expression

描述（由申请人提供）：阿片类药物是现代疼痛治疗的支柱，然而阿片类药物滥用对滥用者和社会产生了重大的负面影响。据估计，目前被监禁的人中有21%是因为与毒品有关的犯罪而入狱。监禁这些人的费用每年高达数百亿美元。由于只有很小比例的阿片类药物使用导致滥用，因此很可能存在一些独特的分子因素，可能使个体易于滥用阿片类药物。本项目将研究吗啡诱导的n -甲基- d -天冬氨酸（NMDA）受体的改变作为阿片类药物滥用倾向的一种潜在机制。NMDA受体与阿片类药物的耐受性、戒断和成瘾过程密切相关。NMDA拮抗剂可以抑制阿片类药物的这些不良反应。然而，单剂量阿片类药物不足以诱导显著的耐受性、戒断或成瘾，这表明为了观察这些后遗症，NMDA受体或神经元回路发生一些变化需要时间。我们发现NMDA受体的NR1和NR2亚基极易受到神经元活动变化的影响，并且NMDA受体的这些变化可能持续很长一段时间。NMDA受体的改变对行为有深远的影响。因此，我们假设吗啡或吗啡戒断在中枢神经系统的不同区域诱导了NR1亚基剪接和NR2亚基的变化。我们进一步假设，一些个体在戒断阿片类药物后很长时间内可能保留这些改变的或“疾病状态”的NMDA受体，这可能导致耐受性延长或戒断症状，并增加对阿片类药物滥用的易感性。在这个项目中，我们将评估吗啡和吗啡戒断对大鼠中枢神经系统不同区域NR1剪接变异体和NR2亚基的影响。我们还将确定这些变化是否在吗啡停药后持续16周。NR1和NR2蛋白将通过western blots和二维western blots进行评估，数据将与两项伤害性试验中的行为相关联。如果数据表明一些个体保留了NMDA受体的疾病状态，则可以设计技术来逆转NMDA受体的变化，以减少这些个体的滥用易感性。

DESCRIPTION (provided by applicant): Opioids are a mainstay of modern pain therapy, yet opioid abuse has a significant negative impact on the abuser and society. It is estimated that 21% of currently incarcerated individuals are in prison because of drug related crimes. The cost to incarcerate these individuals is tens of billions of dollars per year. Since only a small percentage of opioid use results in abuse it is likely that there are some distinguishing molecular factors that may predispose an individual to opioid abuse. This project will investigate morphine induced alterations in N-methyl-D-aspartate (NMDA) receptors as one potential mechanism for predisposition to opioid abuse. NMDA receptors are intimately entwined in the processes of tolerance, withdrawal and addiction to opioids. NMDA antagonists can suppress these adverse effects of opioids. However, a single dose of an opioid is insufficient to induce significant tolerance, withdrawal or addiction indicating that time is required for some change in the NMDA receptors or neuronal circuitry to occur in order to observe these sequelae. We have found that the NR1 and NR2 subunits of NMDA receptors are highly susceptible to alterations as a result of changes in neuronal activity and that these changes in NMDA receptors may persist for an extended period of time. The altered NMDA receptors have a profound effect on behavior. Thus we hypothesize that there are changes in the splicing of NR1 subunits and changes in NR2 subunits that are induced in various regions of the CNS by morphine or morphine withdrawal. We further hypothesize that some individuals may retain these altered or "disease state" NMDA receptors long after withdrawal of the opioid, which may result in prolonged tolerance or withdrawal signs and increased susceptibility to opioid abuse. In this project we will evaluate the effects of morphine and morphine withdrawal on NR1 splice variants and NR2 subunits in various regions of the rat CNS. We will also determine if these changes persist for up to 16 weeks following the withdrawal of morphine. The NR1 and NR2 proteins will be evaluated by western blots and two-dimensional western blots and the data will be correlated to behavior in two nociceptive assays. If the data indicate that some individuals retain the disease state NMDA receptors techniques could be devised to reverse the NMDA receptor changes in an attempt to reduce the abuse susceptibility of these individuals. PUBLIC HEALTH RELEVANCE: N-methyl-D-aspartate (NMDA) receptor antagonists suppress tolerance and addiction to opioids. This project will determine if morphine treatment alters NMDA receptor subunit expression within the CNS and determine if these changes persist in a subgroup of rats. These data could provide clues to novel treatments or novel methods to prevent opioid abuse.