Galanin-opiate interactions

描述（由申请人提供）：我们已经表明，尽管神经肽甘丙肽增强脊髓中的吗啡镇痛，但甘丙肽和甘丙肽激动剂可以拮抗脑中的吗啡强化和戒断。我们的假设是，甘丙肽系统在大脑中通过衰减阿片诱导的多巴胺（DA）信号在腹侧被盖区和脑桥核（Nac）和阿片戒断保护对阿片类药物的强化，并通过下调去甲肾上腺素能信号在蓝斑（LC）和它的目标。因此，甘丙肽激动剂可用于增强阿片镇痛，同时最大限度地减少其滥用倾向。甘丙肽的作用是通过激活G蛋白偶联受体家族（GaIR1、GalR2和GaIR3）介导的。GalR1和GalR2在与药物成瘾相关的大脑区域中表达，例如中脑边缘DA系统和LC，以及在脊髓中表达。GalR1和GalR2的分布和第二信使偶联是不同的，表明它们在甘丙肽神经传递中具有不同的作用。本研究将分析甘丙肽和吗啡在中枢神经系统中的相互作用。我们的第一个目标是确定甘丙肽系统是否通过调节DA系统减弱吗啡位置偏爱，并确定影响吗啡奖赏的甘丙肽受体亚型。我们将确定吗啡诱导的DA释放或吗啡位置偏爱是否在缺乏甘丙肽的小鼠或用全身甘丙肽激动剂Galnon治疗的小鼠中改变。甘丙肽结合将用于确定所使用的任何药理学、行为或遗传操作是否改变GalR水平。第二个目的是确定甘丙肽是否通过调节去甲肾上腺素能系统来减弱阿片类药物戒断，并确定阿片类药物戒断过程中调节的GalR亚型。在去甲肾上腺素能系统中过表达甘丙肽的转基因小鼠将被用于鉴定甘丙肽在这些神经元中调节阿片类药物戒断的作用。使用原位杂交，我们将确定是否GalR1，2和3的mRNA水平的调节慢性吗啡治疗或纳洛酮沉淀在大脑和脊髓中的戒断。我们已经表明，GalR1在LC中阿片类药物戒断后上调，但尚不清楚GalR2或3是否也受到调节。由于没有GalR亚型的选择性拮抗剂，我们还将产生缺乏GalR1的小鼠用于行为研究，以阐明GalR1在阿片镇痛和依赖中的作用。这些实验的目的是表征一个内源性系统，反对阿片奖励和撤退。拟议的研究将确定大脑中参与甘丙肽对这些过程的作用的途径。

DESCRIPTION (provided by applicant): We have shown that although the neuropeptide galanin potentiates morphine analgesia in the spinal cord, galanin and galanin agonists can antagonize morphine reinforcement and withdrawal in the brain. Our hypothesis is that the galanin system in the brain protects against opiate reinforcement by attenuating opiate-induced dopamine (DA) signaling in the ventral tegmental area and nucleus accumbens (Nac) and protects against opiate withdrawal by down-regulating noradrenergic signaling in the locus coeruleus (LC) and its targets. Thus, galanin agonists may be useful for potentiating opiate analgesia while minimizing its abuse liability. The effects of galanin are mediated through activation of a family of G protein-coupled receptors (GaIR1, GalR2 and GaIR3). GalR1 and GalR2 are expressed in brain areas associated with drug addiction, such as the mesolimbic DA system and the LC, as well as in the spinal cord. The distribution and second messenger coupling of GalR1 and GalR2 are distinct, suggesting that they have different roles in galanin neurotransmission. This study will analyze the interactions between galanin and morphine in the CNS. Our first aim is to determine whether the galanin system attenuates morphine place preference by modulating the DA system and to identify the galanin receptor subtypes that affect morphine reward. We will determine whether morphine-induced DA release or morphine place preference is altered in mice lacking galanin or in mice treated with the systemic galanin agonist Galnon. Galanin binding will be used to determine whether any of the pharmacological, behavioral or genetic manipulations used alter GalR levels. The second aim is to determine whether galanin attenuates opiate withdrawal by modulating the noradrenergic system and to identify the GalR subtypes regulated during opiate withdrawal. Transgenic mice over-expressing galanin in the noradrenergic system will be used to identify the role of galanin in these neurons in modulating opiate withdrawal. Using in situ hybridization we will determine whether GalR1, 2 and 3 mRNA levels are regulated by chronic morphine treatment or naltrexone-precipitated withdrawal in brain and spinal cord. We have already shown that GalR1 is upregulated following opiate withdrawal in the LC but it is not known whether GalR2 or 3 are also regulated. Since there are not selective antagonists for GalR subtypes, we will also generate mice lacking GalR1 to use in behavioral studies to elucidate the role of GalR1 in opiate analgesia and dependence. These experiments are designed to characterize an endogenous system that opposes opiate reward and withdrawal. The proposed studies will identify the pathways in the brain involved in galanin's actions on these processes.