Viral-Mediated Alterations in CaMKII Alter Behavioral Responding to Amphetamine

描述（由申请人提供）：反复将大鼠暴露于安非他明（AMPH）等药物可导致运动反应增强，伏隔核（NAcc）多巴胺（DA）溢出和药物服用，当大鼠再次暴露于药物数周至数月后。这些现象，致敏的表现，可能在从偶然使用到滥用药物的过渡中起重要作用。揭示致敏性增强的行为和神经化学反应对药物的表达背后的神经适应性，可能有助于确定治疗干预的目标。钙/钙调素依赖性蛋白激酶II （CaMKII）在介导致敏表达的信号级联反应中发挥重要作用。急性amph诱导的运动反应和NAcc DA释放是钙无关的，而敏化运动和DA释放是钙和camkii依赖的。此外，与暴露于盐水的对照组相比，反复间歇注射AMPH的大鼠纹状体切片显示钙调素水平和CaMKII活性增加。我们假设使用病毒介导的基因转移来改变NAcc中的CaMKII水平将改变对AMPH的行为反应。本拨款申请中提出的实验将测试两个主要假设。假设1:NAcc中CaMKII水平的升高将增强对低阈值AMPH的运动反应，并增强药物的自我给药，其效果与暴露于致敏药物方案的大鼠相似。大鼠将手术植入双侧引导套管和静脉导管。然后进行病毒载体的显微注射，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法确定。假设2：致敏大鼠NAcc中CaMKII无活性突变形式水平的增加将削弱这些大鼠观察到的增强的AMPH自我给药。大鼠将暴露于反复，间歇性注射AMPH，随后是一段停药期，在此期间动物将准备手术。在一段时间的自我给药后，将进行病毒载体的显微注射，并随后评估这种操作对药物自我给药的影响。使用成瘾动物模型是研究从偶然到强迫性药物使用过渡的有效方法。本研究将通过研究如何防止在先前暴露于AMPH的大鼠中观察到的药物服用增强，从而有助于预防药物成瘾的最终目标。

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.