Galanin-opiate interactions

描述（由申请人提供）：我们已经证明，尽管神经肽甘丙肽在脊髓中增强吗啡镇痛，但甘丙肽和甘丙肽激动剂可以拮抗吗啡在大脑中的强化和戒断。我们的假设是，大脑中的甘丙氨酸系统通过减弱腹侧被盖区和伏隔核（Nac）中阿片诱导的多巴胺（DA）信号来保护阿片强化，并通过下调蓝斑（LC）及其靶点的去甲肾上腺素能信号来保护阿片戒断。因此，丙氨酸激动剂可能有助于增强阿片类镇痛，同时尽量减少其滥用的可能性。甘丙氨酸的作用是通过激活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，如中脑边缘DA系统和LC以及脊髓中表达。GalR1和GalR2的分布和第二信使偶联是不同的，表明它们在galanine神经传递中有不同的作用。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系统减弱吗啡的位置偏好，并确定影响吗啡奖励的甘丙肽受体亚型。我们将确定吗啡诱导的DA释放或吗啡位置偏好是否会在缺乏丙氨酸的小鼠或接受系统性丙氨酸激动剂加农治疗的小鼠中发生改变。gal丙氨酸结合将用于确定是否使用任何药理学，行为或遗传操作来改变GalR水平。第二个目的是确定丙氨酸是否通过调节去肾上腺素能系统来减轻阿片戒断，并确定在阿片戒断期间调节的GalR亚型。在去甲肾上腺素能系统中过度表达丙氨酸的转基因小鼠将被用来确定丙氨酸在这些神经元中调节阿片戒断的作用。使用原位杂交，我们将确定GalR1, 2和3mrna水平是否受慢性吗啡治疗或纳曲酮沉淀戒断脑和脊髓的调节。我们已经证明GalR1在阿片类药物戒断后上调，但GalR2或gal3是否也受到调节尚不清楚。由于GalR亚型没有选择性拮抗剂，我们也将产生缺乏GalR1的小鼠用于行为学研究，以阐明GalR1在阿片类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，反对阿片类奖赏和戒断。拟议的研究将确定大脑中参与甘丙肽在这些过程中的作用的途径。

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.