The Role of Hypothalamic H3 Histamine Receptors in Regulation of Striatal Function

过敏性炎症与许多表现为纹状体损害的神经精神障碍有关。 失调，包括自闭症、强迫症和精神分裂症。但 这些联系背后的机制仍不清楚。对纹状体功能的一种可能影响是 外周免疫介质组胺。组胺不仅是过敏性免疫反应的关键介质， 也是一种中枢神经递质神经递质组织胺仅由后部 下丘脑结节乳头核（TMN）。组胺能神经元共同释放GABA;它们 神经支配纹状体，在那里它们维持紧张性抑制以抑制纹状体过度活跃。 在缺乏组胺的遗传小鼠系，组氨酸脱羧酶（Hdc）敲除小鼠中的观察， 表明全身组胺和纹状体活动之间可能存在联系。Hdc-KO小鼠表现出 组胺自身受体H3 R的上调，特别是在TMN中，并且具有更大的基线神经元特异性。 纹状体的活动。H3 R受体的系统活化促进进一步增强的纹状体活性。在 在野生型小鼠中，TMN的化学遗传沉默也增强了纹状体活性。下丘脑是 被允许系统免疫信号相对自由通过的室周器官包围， 组胺。我们假设全身组胺通过H3 R直接调节TMN活性， 调节纹状体中的下游活动。 第一个目的是测试Hdc-KO小鼠中TMN中H3 R上调是否介导全身免疫调节的作用。 给予H3 R激动剂RAMH对纹状体活性的影响。这将为今后的工作提供信息， 组胺来源于TMN和纹状体上下丘脑内的肥大细胞和其他过敏性免疫细胞 活动将RAMH靶向递送至TMN将测试TMN H3 R活化诱导纹状体细胞凋亡的充分性。 TMN中H3 R的过度活跃和shRNA靶向下调将测试这些受体的必要性。 在WT和Hdc-KO小鼠中介导全身RAMH后的纹状体活动过度。第二个目标测试 TMN中H3 R的过表达是否足以重现所观察到的纹状体活性表型 在Hdc-KO小鼠中，这将进一步支持下丘脑H3 R在调节纹状体活性中的重要性 表型最后，在目标3中，我测试过敏性炎症是否影响TMH和TMH中的神经活动。 纹状体，以及这是否是由下丘脑H3 R介导的。 本文的工作为进一步研究TMN及其下游的免疫控制奠定了基础 脑靶点，与广泛的神经精神疾病有潜在的相关性。

Allergic inflammation is associated with a number of neuropsychiatric disorders exhibiting striatal dysregulation, including autism, obsessive-compulsive disorder, and schizophrenia. However, the mechanisms underlying these links remain unknown. One possible influence on striatal function is the peripheral immune mediator histamine. Histamine is not only a key mediator of the allergic immune response, but is also a central neurotransmitter. Neurotransmitter histamine is produced solely by the posterior tuberomammillary nucleus (TMN) of the hypothalamus. Histaminergic neurons co-release GABA; they innervate the striatum, where they maintain tonic inhibition to suppress striatal hyperactivity. An observation in a genetic mouse line lacking histamine, the histidine decarboxylase (Hdc) knockout mouse, suggests a possible connection between systemic histamine and striatal activity. Hdc-KO mice exhibit upregulation of the histamine autoreceptor H3R, particularly in the TMN, and have greater baseline neuronal activity in the striatum. Systemic activation of the H3R receptor promotes further enhanced striatal activity. In wild-type mice, chemogenetic silencing of the TMN also enhanced striatal activity. The hypothalamus is surrounded by circumventricular organs which allow relatively free passage of systemic immune signals, such as histamine. We hypothesize that systemic histamine directly modulates TMN activity via H3R and thereby regulates downstream activity in the striatum. The first Aim tests whether H3R upregulation in the TMN in Hdc-KO mice mediates the effects of systemic administration of the H3R agonist RAMH on striatal activity. This will inform future work exploring the effects of histamine derived from mast cells and other allergic immune cells within the hypothalamus on TMN and striatal activity. Targeted delivery of RAMH to the TMN will test the sufficiency of TMN H3R activation to induce striatal hyperactivity, and shRNA-targeted downregulation of H3R in the TMN will test the necessity of these receptors in mediating striatal hyperactivity after systemic RAMH in both WT and Hdc-KO mice. The second Aim tests whether overexpression of H3R in the TMN is sufficient to recapitulate the striatal activity phenotype observed in Hdc-KO mice, which would further support the importance of hypothalamic H3R in modulating striatal activity phenotypes. Finally, in Aim 3, I test whether allergic inflammation affects neural activity in the TMH and the striatum, and whether this is mediated by hypothalamic H3R. This work will lay the groundwork for further investigations of immune control of the TMN and downstream brain targets, with potential relevance to a wide spectrum of neuropsychiatric disorders.