Regulation of Addictive Behavior by Dopamine Signaling

描述（由申请人提供）：从药物使用过渡到成瘾状态的信号是药物摄入的显著增加和戒断期间寻求药物的增加。我们的研究表明，长期吸毒后伏隔核（NAc） cAMP/PKA信号通路的上调直接促成了这种转变，可能是通过改变D1和D2受体介导的调节吸毒和寻求行为的反应。为了验证这一假设，研究测量了低摄入量和高摄入量大鼠慢性自我服用可卡因之前、期间和之后的Dl和D2受体反应性。行为研究追踪Dl和D2运动调节的敏感性（非条件反应）和可卡因寻求的复发（条件反应）与时间和个体升级倾向的关系。平行的生化研究追踪下游camp依赖蛋白磷酸化和相关信号蛋白在慢性可卡因自我给药之前、期间和之后的变化，以比较低和高摄入量大鼠及其对照伙伴。在三种不同的cAMP/PKA上调模型中，研究了cAMP/PKA信号上调的功能后果。第一种模型在大鼠NAc核壳亚区微量注射霍乱毒素。另外两种模型利用可诱导的转基因小鼠在含有Dl/dynorphin-或D2/enkephalin-的纹状体神经元中过表达Gs蛋白。这些研究将测试不同NAc亚区和特定纹状体细胞类型的cAMP/PKA上调对可卡因摄入量增加、药物、线索和压力诱导的可卡因寻求长期复发的相对贡献。研究还探讨了cAMP/PKA上调在运动和复发中d1和D2受体反应性改变中的作用，下游cAMP依赖蛋白磷酸化是生化相关的。NAc中的AMPA谷氨酸受体可能通过与D1和D2调节的cAMP/PKA信号通路的特异性相互作用来调节成瘾行为。这些相互作用是通过病毒介导的GluRl和GluR2 AMPA亚基在NAc神经元中的过表达来研究的，用于可卡因自我给药和可卡因寻求复发的实验。研究还使用PKA不敏感的GluR1载体测试了特异性AMPA受体与D1和D2受体在运动和复发调节中的相互作用，以及它们对cAMP/PKA信号的依赖性。总之，这些研究结合了相关的行为模型和现代分子技术来研究导致成瘾过程的离散神经和行为改变

DESCRIPTION (provided by applicant): The transition from drug use to an addicted state is signaled by marked escalation in drug intake and increased drug seeking during withdrawal. Our studies suggest that up-regulation in cAMP/PKA signaling pathways in nucleus accumbens (NAc) following chronic drug use directly contributes to this transition, possibly by differentially altering D1 and D2 receptor-mediated responses that regulate drug-taking and -seeking behaviors. To investigate this hypothesis, studies measure Dl and D2 receptor responsiveness before, during and after chronic cocaine self-administration in Low and High intake rats. Behavioral studies track sensitivity to Dl and D2 regulation of locomotion (unconditioned responses) and relapse to cocaine seeking (conditioned responses) in relation to both time and individual propensity for escalation. Parallel biochemical studies track changes in downstream cAMP-dependent protein phosphorylation and related signaling proteins before, during and after chronic cocaine self-administration, for comparison in Low and High intake rats and their yoked partners. The functional consequence of up-regulation in cAMP/PKA signaling is studied in three anatomically distinct models of cAMP/PKA up-regulation. The first model utilizes cholera toxin microinfusion in NAc core and shell subregions in rats. The other two models utilize inducible transgenic mice that over-express Gs proteins in either Dl/dynorphin- or D2/enkephalin-containing striatal neurons. These studies will test the relative contribution of cAMP/PKA up-regulation in distinct NAc subregions and specific striatal cell types to escalating cocaine intake, long-term relapse to cocaine seeking induced by drugs, cues, and stress. Studies also investigate the role of cAMP/PKA up-regulation on altered D 1 and D2 receptor responsiveness in locomotion and relapse, with downstream cAMP-dependent protein phosphorylation as a biochemical correlate. AMPA glutamate receptors in NAc may regulate addictive behavior via specific interactions with D1- and D2- regulated cAMP/PKA signaling pathways. These interactions are studied using viral-mediated over-expression of GluRl and GluR2 AMPA subunits in NAc neurons in assays of cocaine self-administration and relapse to cocaine seeking. Studies also test specific AMPA receptor interactions with D1 and D2 receptors in regulation of locomotion and relapse, and their dependence on cAMP/PKA signaling using a PKA insensitive GluR1 vector. Together, these studies combine relevant behavioral models with modem molecular techniques to investigate discrete neural and behavioral alterations that contribute to the addiction process