Regulation of Addictive Behavior by Dopamine Signaling

描述(由申请人提供)：从吸毒到上瘾状态的转变标志着吸毒量的显著增加和戒毒过程中寻求毒品的增加。我们的研究表明，慢性药物使用后伏隔核(NAC)cAMP/PKA信号通路的上调直接导致了这种转变，可能是通过不同地改变D1和D2受体介导的调节药物摄取和寻找行为的反应。为了研究这一假说，研究测量了低和高摄入量的大鼠在长期服用可卡因之前、期间和之后的DL和D2受体反应性。行为学研究跟踪了对DL和D2运动调节的敏感性(无条件反应)和对寻求可卡因的复发(条件反应)与时间和个人升级倾向的关系。平行的生化研究跟踪下游cAMP依赖的蛋白磷酸化和相关信号蛋白在长期服用可卡因之前、期间和之后的变化，以比较低和高摄入量的大鼠及其连接的伙伴。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。第一种模型采用大鼠NAC核心区和壳区微量注射霍乱毒素。另外两个模型利用可诱导的转基因小鼠，在含有D1/强啡肽或D2/脑啡肽的纹状体神经元中过表达Gs蛋白。这些研究将测试不同的NAC亚区和特定纹状体细胞类型中cAMP/PKA上调在药物、线索和应激诱导的可卡因摄入量增加、长期复发方面的相对贡献。研究还探讨了cAMP/PKA上调对D1和D2受体反应性改变在运动和复发中的作用，下游cAMP依赖的蛋白磷酸化是一种生化相关。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。通过病毒介导的GluR1和GluR2 AMPA亚基在NAC神经元中的过度表达，研究了这些相互作用在可卡因自我给药和复吸可卡因寻找中的作用。研究还利用PKA不敏感的GluR1载体测试了AMPA受体与D1和D2受体在调节运动和复发方面的特异性相互作用，以及它们对cAMP/PKA信号的依赖性。总之，这些研究将相关的行为模型与现代分子技术相结合，研究导致成瘾过程的离散的神经和行为变化

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