Endocannabinoids regulate microglia in developing brain

 说明(由申请人提供)：在大麻非刑事化、医学化和在某些情况下合法化之后，改变对大麻使用的看法可能会增加孕妇使用大麻的安全感。内源性大麻素是CB1和CB2受体的内源性配体，大麻的成分在这些受体上发挥作用，改变神经功能。内源性大麻素在调节大脑发育中的作用知之甚少，但这些神经调节剂在胎儿生命中普遍存在并在相对较早的时间表达。大脑中的性别差异在生命早期也被确立，在实验室动物模型中，内源性大麻素被认为是发育中的杏仁核细胞数量的基本中介。最近，小胶质细胞，大脑中专门的免疫细胞，也被认为是大脑性别差异的重要媒介。这些观察使我们探索了内源性大麻素是否调节了小胶质细胞的活动，并导致了令人惊讶的发现，发育中的杏仁核吞噬活性的性别差异是由CB1(可能是CB2)受体激活所介导的。更令人惊讶的是，对小胶质细胞吞噬杯内容物的鉴定表明，成熟的和新生的活神经元都被吞噬了。因此，小胶质细胞似乎以性别特有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体功能不可或缺的一部分，其中许多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特定的目标来建立这些新的观察基础上，这将1)充分表征内源性大麻素对发育中的雄性和雌性大鼠幼鼠杏仁核和海马区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底物，以及3)建立内源性大麻素介导的吞噬作用与受杏仁核或海马体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交游戏行为、压力和焦虑反应以及学习和记忆的方面。使用的方法包括免疫组织化学、细胞出生日期测定、流式细胞术、给药和广泛的行为测试。这些研究的完成将阐明内源性大麻素在两个关键脑区--海马体和杏仁体--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研究提供基础。

 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.