Microglial pruning of dopamine receptors and opioid abuse.

多巴胺能“奖赏”回路经历了显著的发育可塑性 青春期，包括多巴胺D_1和D_2(D_1/D_2R)受体在 伏核(NAC)。我们最近在雄性大鼠身上证明了小胶质细胞-- 中枢神经系统的初级免疫细胞，也在塑造发育回路中发挥作用-吞噬和 在青少年NAC发育的精确窗口中消除D1Rs对受体的反应 小胶质细胞对D1Rs的这种发育修剪是通过补体蛋白C3进行的 对正常的奖励驱动行为(社交游戏)的发展至关重要。此外，老鼠 在青春期反复服用吗啡(但不是青春期)表现出持久性 成年后小胶质细胞功能的变化和对吗啡的恢复增加； 在青少年吗啡暴露期间使用神经胶质调节剂可以防止这种增加 恢复，暗示了小胶质细胞的关键作用。小胶质细胞提炼突触基于 神经活动的变化，使我们假设，在男性中，(1)小胶质细胞雕刻NAC D1r 在正常青春期，由于多巴胺(DA)活动的改变，导致 由“Eat Me”信号C3标记的受体；以及(2)显著影响DA信号的因素 在青春期的NAC中可能会持续地改变奖赏过程--包括成瘾 易损性-通过改变D1r的小胶质细胞修剪。我们将使用3个目标来检验假设 多巴胺能进入NAC导致D1R的补体C3“标记”和吞噬 小胶质细胞和这种正常输入的中断(例如，由于社会隔离压力)将导致 不规范的长期奖励驱动行为。重要的是，D1R精化通过 女性中不依赖小胶质细胞-C3相互作用的未知机制及其意义 上瘾的原因还没有得到评估。为了探索女性的假设机制，我们将 此外，评估D2R的变化，并检查其他假定的分子标签/“Eat-Me” 信号。

The dopaminergic “reward” circuitry undergoes significant developmental plasticity during adolescence, including the refinement of dopamine D1 and D2 (D1/D2r) receptors within the nucleus accumbens (NAc). We have recently demonstrated in male rats that microglia – the primary immune cells of the CNS that also play a role in sculpting developing circuits – engulf and eliminate D1rs during a precise window of adolescent NAc development in response to receptor “tagging” by complement protein C3; and that this developmental pruning of D1rs by microglia is critical for the development of normal reward-driven behavior (social play). Moreover, rats that receive repeated morphine during adolescence (but not young adulthood) show persistent changes in microglial function and increased reinstatement to morphine as adults; and, pre- treatment with a glial modulator during adolescent morphine exposure prevents this increased reinstatement, implicating a critical role for microglia. Microglia refine synapses based on changes in neural activity, leading us to hypothesize that, in males (1) microglia sculpt NAc D1rs during normal adolescence as a consequence of altered dopamine (DA) activity which leads to receptor tagging by the “eat me” signal C3; and (2) factors that significantly impact DA signaling within the NAc during adolescence could persistently alter reward processing - including addiction liability - by changing microglial pruning of D1rs. We will use 3 aims to test the hypothesis that dopaminergic input to the NAc leads to complement C3 “tagging” of D1r and phagocytosis by microglia and that disruptions of this normal input (e.g. by social isolation stress) will lead to dysregulated long-term reward-driven behaviors. Importantly, D1r refinement occurs via unknown mechanisms in females, independent of microglia-C3 interaction, and the implications for addiction have not been assessed. To explore putative mechanisms in females we will additionally assess changes in D2r, and examine additional putative molecular tags/ “eat-me” signals.