Viral-Mediated Alterations in CaMKII Alter Behavioral Responding to Amphetamine

描述(由申请人提供)：反复暴露于安非他明(Amph)等药物会导致大鼠运动反应增强，伏隔核(NAcc)多巴胺(DA)溢出，当大鼠几周至几个月后再次暴露于药物时，会导致吸毒。这些现象是敏感化的表现，可能在从偶尔吸毒向滥用的过渡过程中发挥重要作用。解开神经适应的基础表达敏化--增强对药物的行为和神经化学反应--可能有助于确定治疗干预的目标。钙/钙调蛋白依赖的蛋白激酶II(CaMKII)在介导致敏表达的信号级联反应中起着重要作用。AMPH诱导的急性运动反应和NAcc DA释放不依赖于钙离子，而敏化运动和DA释放依赖于钙和CaMKII。此外，与生理盐水对照组相比，反复间歇注射amph的大鼠纹状体切片显示钙调蛋白水平和CaMKII活性增加。我们假设，使用病毒介导的基因转移来改变NAcc中CaMKII的水平将改变对AMPH的行为反应。这项拨款申请中提出的实验将检验两个主要假设。假设1：NAcc中CaMKII水平的增加将增强对低阈值剂量AMPH的运动反应，并增强药物的自我给药，效果类似于在暴露于致敏药物方案的大鼠中观察到的效果。大鼠将通过手术植入双侧导尿管和静脉导管。然后将进行病毒载体的微量注射，并进行运动和自我给药实验，以确定这种操作如何改变对Amph的敏感性。病毒介导的基因转移的效果将通过免疫印迹来确定。假设2：在致敏大鼠的NAcc中，增加CaMKII的非活性突变形式的水平将减少在这些大鼠中观察到的增强的Amph自我给药。大鼠将接受反复间歇注射AMPH，然后是一段戒断期，在此期间，动物将接受手术准备。在药物自我给药一段时间后，将进行病毒载体的显微注射，并随后评估这种操纵对药物自我给药的影响。使用上瘾的动物模型是研究从随意吸毒到强制吸毒的转变的有效方法。这项研究将通过研究防止在先前暴露于amph的大鼠身上观察到的增加吸毒的方法，为预防药物成瘾的最终目标做出贡献。

DESCRIPTION (provided by applicant): Repeatedly exposing rats to drugs such as amphetamine (AMPH) can lead to enhanced locomotor responding, nucleus accumbens (NAcc) dopamine (DA) overflow and drug taking when rats are re-exposed to the drug weeks to months later. These phenomena, manifestations of sensitization, may play an important role in the transition from casual drug use to abuse. Unraveling the neuroadaptations that underlie the expression of sensitization-enhanced behavioral and neurochemical responding to the drug-- may help identify targets for therapeutic intervention. One of many proteins that play an important role in mediating signaling cascades underlying the expression of sensitization is calcium/calmodulin-dependent protein kinase II (CaMKII). While acute AMPH-induced locomotor responding and NAcc DA release are calcium-independent, sensitized locomotion and DA release are calcium and CaMKII-dependent. In addition, striatal slices from rats exposed to repeated, intermittent injections of AMPH show enhanced calmodulin levels and increased CaMKII activity compared to those obtained from saline-exposed controls. We hypothesize that using viral-mediated gene transfer to modify CaMKII levels in the NAcc will alter behavioral responding to AMPH. The experiments proposed in this grant application will test two main hypotheses. Hypothesis 1: Increasing levels of CaMKII in the NAcc will enhance locomotor responding to a low, threshold dose of AMPH and enhance self-administration of the drug, effects similar to those observed in rats exposed to a sensitizing drug regimen. Rats will be surgically implanted with bilateral guide cannulae and intravenous catheters. Microinjections of the viral vectors will then be made and locomotor and self- administration experiments will be conducted to determine how this manipulation alters sensitivity to AMPH. The efficacy of viral-mediated gene transfer will be determined using immunoblotting. Hypothesis 2: Increasing levels of an inactive mutant form of CaMKII in the NAcc of sensitized rats will diminish enhanced AMPH self-administration observed in these rats. Rats will be exposed to repeated, intermittent injections of AMPH followed by a withdrawal period, during which the animals will be surgically prepared. Following a period of drug self-administration, microinjections of the viral vectors will be made and the effect of this manipulation on drug self-administration subsequently assessed. Using an animal model of addiction is an effective way to study the transition form casual to compulsive drug use. This research will contribute to the ultimate goal of preventing drug addiction by investigating ways to prevent the enhanced drug taking observed in rats that have been previously exposed to AMPH.