Endocannabinoids regulate microglia in developing brain

 描述（由申请人提供）：在大麻合法化、医疗化和在某些情况下合法化之后，对大麻使用的看法发生变化，这可能会增加孕妇对使用安全性的看法。内源性大麻素是CB1和CB2受体的内源性配体，大麻的成分作用于CB1和CB2受体以改变神经功能。内源性大麻素在介导大脑发育中的作用知之甚少，然而这些神经调节剂在胎儿生命中相对较早地分布和表达。大脑中的性别差异也在生命早期建立，在实验室大鼠动物模型中，内源性大麻素被认为是发育中的杏仁核中细胞数量的重要介质。最近，小胶质细胞，大脑的专门免疫细胞，也被认为是大脑性别差异的重要介质。这些观察结果使我们探索内源性大麻素是否调节小胶质细胞的活性，并导致在发育中的杏仁核中由CB1（可能还有CB2）受体激活介导的吞噬活性的性别差异的惊人发现。更令人惊讶的是，小胶质细胞吞噬杯的内容物的鉴定表明成熟和新生的活神经元都被吞噬。因此，小胶质细胞似乎以性别特异性的方式控制细胞数量和表型，性别差异的来源是内源性大麻素。我们还观察到海马体细胞发生的性别差异，但方向与杏仁核相反。内源性大麻素是海马功能不可或缺的一部分，其中大部分在男性和女性中是不同的，但这是否与细胞发生有关尚不清楚。我们现在建议通过完成三个具体目标来建立这些新的观察结果，这三个目标将1）充分表征内源性大麻素对雄性和雌性大鼠幼仔发育中的杏仁核和海马体中的小胶质细胞吞噬活性的影响，2）更彻底地识别被小胶质细胞吞噬的细胞基质，和3）建立内源性大麻素介导的吞噬作用与由杏仁核或海马控制并受性别影响的行为之间的相关性。这些包括青少年的社会游戏行为，压力和焦虑反应以及学习和记忆方面。使用的方法包括免疫组织化学，细胞出生日期，流式细胞术，药物管理，和广泛的行为测试。这些研究的完成将阐明内源性大麻素在海马体和杏仁核这两个关键大脑区域发育中的作用，并为今后关于怀孕期间使用大麻及其对男性和女性大脑发育的影响的工作奠定基础。

 DESCRIPTION (provided by applicant): Changing views on cannabis use subsequent to decriminalization, medicalization and in some cases legalization is likely to increase perceptions of safety for use by pregnant women. The endocannabinoids are the endogenous ligands for the CB1 and CB2 receptors on which components of cannabis act to alter neural function. The role of endocannabinoids in mediating brain development is poorly understood, yet these neural modulators are ubiquitously distributed and expressed relatively early in fetal life. Sex differences in the brain are also established early in life and endocannabinoids have been implicated as essential mediators of cell number in the developing amygdala in the laboratory rat animal model. More recently, microglia, specialized immune cells of the brain, have also been implicated as essential mediators of sex differences in the brain. These observations led us to explore whether endocannabinoids modulate microglial activity and resulted in the surprising discovery of sex differences in phagocytic activity in the developing amygdala that is mediated by CB1 (and possibly CB2) receptor activation. Even more surprising, identification of the contents of microglial phagocytic cups suggests the engulfment of both mature and newly born live neurons. Thus microglia appear to be controlling both cell number and phenotype in a sex-specific manner, with the source of the sex difference being endocannabinoid tone. We have also observed a sex difference in cell genesis in the hippocampus but in the opposite direction to that of the amygdala. Endocannabiniods are integral to hippocampal functioning, much of which is different in males and females, but whether this relates to cell genesis is unknown. We now propose to build on these novel observations via completion of three specific aims which will 1) fully characterize the effect of endocannabinoids on microglial phagocytic activity in the developing amygdala and hippocampus of male and female rat pups, 2) more thoroughly identify the cellular substrates being engulfed by microglia, and 3) establish a correlation between endocannabinoid mediated phagocytosis and behaviors which are controlled by the amygdala or hippocampus and impacted by sex. These include juvenile social play behavior, stress and anxiety responding and aspects of learning and memory. Approaches used include immunohistochemistry, cell birth dating, Flow cytometery, drug administration, and extensive behavioral testing. Completion of these studies will elucidate the role of endocannabinoids in development of two key brain areas, the hippocampus and amygdala, and provide the foundations for future work on cannabis use during pregnancy and its impact on the developing brain of both males and females.