Roles of kainate receptors in behavioral plasticity rela

红藻氨酸受体（KARs）调节谷氨酸和GABA的释放以及参与情绪调节的不同脑区（包括前扣带皮层、海马和杏仁核）中的突触可塑性。KAR家族包括五个亚基：GluR 5 -7和KA-1-2（也分别称为谷氨酸受体离子型红藻氨酸盐（GRIK）1-5）。受体形成异三聚体或同源三聚体（仅GluR 5 -7）。GluR 5和GluR 6可以进行RNA编辑，从而改变通道对不同离子的渗透性。不同KAR亚基的细胞表面表达受受体转录物的选择性剪接和受体亚型的运输特性的调节。GluR 6基因位于染色体6q16.3-q21上，该区域已被暗示在一些双相情感障碍连锁研究中。最近的遗传关联研究直接暗示GluR 6是增加情绪障碍风险的一个因素。然而，红藻氨酸受体在情绪调节中的作用在很大程度上是未知的。因此，我们在GluR 5和GluR 6敲除（KO）和野生型对照小鼠中进行了研究，使用情绪障碍和神经化学实验的行为测试电池。 GluR 5和6 KO小鼠似乎达到正常生长，并且没有神经异常。与WT和GluR 5 KO小鼠相比，GluR 6 KO消耗更多的糖精甜味剂溶液，这是享乐活动的指标。GluR 6 KO旅行更长的距离，进入并花费更多的时间在开放领域的中心（这可以作为一般活动以及探索性冒险活动的指标）。GluR 6 KO的过度活跃在整个实验期间持续存在，并且它们没有表现出对开放场地竞技场的习惯。GluR 6 KO在社交互动和居民入侵者测试中都表现出攻击性。GluR 6 KO在高架十字迷宫的开放臂中具有更多的活性，而在强迫游泳测试中具有较少的不动性。GluR 6 KO在安非他明攻击试验中也表现出更高的反应。总之，GluR 6基因敲除小鼠在整个实验过程中表现出行为兴奋、更强的攻击性和快感过度;这些似乎是临床躁狂状态的表型。此外，长期锂治疗减轻了GluR 6 KO小鼠的关键行为改变，包括提高运动活性，加重攻击性和对苯丙胺的超敏感性。因此，这些数据强烈支持GluR 6神经传递是情绪相关行为的关键调节剂的观点，并且GluR 6神经传递的遗传功能障碍可以导致躁狂样行为的行为表现。未来的研究需要阐明人类GluR 6 SNP对GluR 6功能和相关神经传递的影响，参与GluR 6介导的情绪样行为可塑性的脑区，以及GluR 6作为开发情绪影响剂的新靶点。

Kainate receptors (KARs) regulate the release of glutamate and GABA and synaptic plasticity in different brain regions involved in mood regulation, including the anterior-cingulate cortex, hippocampus, and amygdala. The KAR family includes five subunits: GluR5-7 and KA-1-2 (also called glutamate receptor ionotropic kainate (GRIK) 1-5 respectively). The receptors form hetereotrimers or homotrimers (GluR5-7 only). GluR5 and 6 can undergo RNA editing, resulting in altered channel permeability to different ions. The cell surface expression of the different KAR subunits is regulated by alternative splicing of receptor transcripts and trafficking properties of the receptor subtypes. The GluR6 gene is on chromosome 6q16.3-q21, a region of which has been implied in several bipolar disorder linkage studies. Recent genetic association studies directly implicates GluR6 as a contributing factor to increased risk of mood disorders. However, the roles of kainate receptors in mood regulation are largely unknown. Therefore we conducted studies in GluR5 and GluR6 knockout (KO) and wild-type control mice using a behavioral test battery for mood disorders and neurochemical experiments. GluR5 and 6 KO mice appeared to attain normal growth, and lacked neurological abnormalities. Compared to WT and GluR5 KO mice, GluR6 KO consumed more saccharin sweeten solution, an indicator of hedonic activity. GluR6 KO traveled longer distances, entered and spent more time in the center of the open field (which can serve as indices for general activity as well as explorative-risk-taking activities). The hyperactivity of GluR6 KO persisted throughout the entire experimental period and they showed no habituation to the open-field arena. GluR6 KO exhibited aggressiveness in both the social interaction and resident-intruder tests. GluR6 KO had more activity in the open-arm of an elevated plus maze and less immobility in the forced swim test. GluR6 KO also exhibited higher responses in amphetamine challenge test. In summary, GluR6, but not GluR5, KO mice display behavioral excitement throughout experiments, greater aggressiveness, and hyperhedonia; these appear to phenocopy of the clinical manic state. Furthermore, chronic lithium treatment relieved key behavioral alterations of GluR6 KO mice including heightened locomotor activity, aggravated aggression and supersensitivity to amphetamine. Thus, the data strongly support the notion that GluR6 neurotransmission is a critical modulator of mood related behavior and that genetic dysfunction of GluR6 neurotransmission can result in behavioral display of mania-like behavior. Future studies are needed to elucidate the effects of human GluR6 SNPs on the function of GluR6 and related neurotransmission, brain regions involved in GluR6 medicated mood-like behavioral plasticity, and GluR6 as novel targets for developing mood affecting agents.