Function of galanin receptor subtypes in the hippocampus

描述(申请人提供)：甘丙肽，一种广泛表达的神经肽， 当脑室内应用时，会损害认知能力，抑制 癫痫发作活动，并影响性行为和进食行为。这些 至少三种已知的G蛋白具有不同的药理作用 偶联受体：GALR1、GALR2和GALR3。甘丙肽的体内效应有 通过使用甘丙肽和一些高亲和力嵌合体来确定 甘丙肽拮抗剂，M15，M35和M40，我们介绍了。这些配体缺乏 受体亚型选择性，因此特定甘丙素的贡献 受体亚型对甘丙素在体内的多种作用尚不清楚。这个 连接到不同甘丙素激活的第二信使系统 已经在转基因的非神经细胞中研究了受体亚型，留下了 怀疑同样的信号是否发生在海马神经元中 这些受体有自己的一套G蛋白。在这项研究中，我们希望 确定在CA1锥体细胞中表达的GALR1的作用，以及 在齿状回颗粒细胞中表达的GALR2信号转导通路 这些神经元。我们将研究CREB和MAPK通路以及海马区 兴奋性，包括齿状回和CA1区的LTP，这两个区域是 甘丙氨酸明显抑制。在缺乏受体亚型特异性的情况下 配体，为了确定特定甘丙素受体亚型的作用，我们将 利用GALR1(-/-)转基因小鼠并在体内下调GALR1 细胞穿透性多肽核酸(PNA)型表达GALR2 脑室应用反义寡核苷酸。最后，亚型(S)特异性 突触前甘丙素受体调节去甲肾上腺素(NE)、谷氨酸和 海马区乙酰胆碱(ACh)的释放将在 微透析实验。我们假设甘丙素作用于GALR1和 GALR2受体抑制海马区兴奋性 癫痫发作阈值和认知功能。预计结果将是 为理解不同甘丙素受体的作用奠定基础 认知中的亚型，并将这些甘丙素受体亚型定义为假定的 以药物为靶点的认知能力增强药物。此外，这些 甘丙肽受体亚型参与神经元放电的调节 大脑中的5-羟色胺能和去甲肾上腺素能细胞，以及关于 它们在海马体中的作用机制可能有助于理解 它们在这些单胺能系统中的作用以及在抑郁症中的作用。还有，因为 甘丙肽已被证明具有抗癫痫作用，了解这是如何 多肽调节癫痫发作可能在临床治疗中的应用 癫痫。

DESCRIPTION (provided by applicant): Galanin, a broadly expressed neuropeptide, when applied intracerebroventricularly impairs cognitive performance, dampens seizure activity, and affects sexual activity and feeding behaviors. These diverse pharmacological effects are exerted by at least three known G protein coupled receptors: GALR1, GALR2, and GALR3. The in vivo effects of galanin have been determined by using the peptide galanin and some high affinity chimeric galanin antagonists, M15, M35 and M40, which we introduced. These ligands lack receptor subtype selectivity, and thus the contribution of the specific galanin receptor subtypes to the multiple in vivo effects of galanin is not known. The second messenger systems coupled to activation of the different galanin receptor subtypes have been studied in transfected non-neuronal cells, leaving in doubt whether the same signaling occurs in hippocampal neurons expressing these receptors with their own set of G-proteins. In this study we wish to determine the contribution of GALR1, expressed in pyramidal cells of CA1, and of GALR2, expressed in the granule cells in the dentate gyrus, to signaling in these neurons. We will examine CREB and MAPK pathways and hippocampal excitability, including LTP in the dentate gyrus and CA1 regions, which are markedly depressed by galanin. In the absence of receptor subtype-specific ligands, to determine the roles of specific galanin receptor subtypes we will utilize the GALR1 (-/-) transgenic mice and in vivo down regulation of GALR1 and GALR2 expression by cell penetrating peptide nucleic acid (PNA) type antisense oligonucleotides applied icv. Finally, the subtype(s) specificity of presynaptic galanin receptors that regulate noradrenaline (NE), glutamate and acetylcholine (ACh) release in the hippocampus will be addressed in microdialysis experiments. We hypothesize that galanin acting at GALR1 and GALR2 receptors suppresses hippocampal excitability with consequences for seizure threshold and cognitive function. It is expected that the results will form the basis for understanding the role of different galanin receptor subtypes in cognition, and define these galanin receptor subtypes as putative drug targets for cognitive performance-enhancing drugs. Furthermore, these galanin receptor subtypes participate in the regulation of the firing of serotonergic and noradrenergic cells in the brain, and information regarding their mechanism of action in the hippocampus may contribute to understanding their effects in these monoaminergic systems, and in depression. Also, because galanin has been shown to have anti-epileptic actions, understanding how this peptide regulates seizures could have clinical applications in the treatment of epilepsy.