Single-nucleus RNA sequencing of striatal microglia reveals distinct transcriptomic signatures of acute stress and chronic exercise
Acute stress has enduring effects on the brain and motivated behavior across species. For example, acute stress produces persisting decreases in voluntary physical activity as well as molecular changes in the striatum, a brain region that regulates voluntary physical activity and other motivated behaviors. Microglia, the primary immune cells of the central nervous system, are positioned at the interface between neural responses to stress and neural coordination of voluntary activity in that they respond to stress, sense molecular changes in the striatum, and modulate neuronal activity. However, the role of striatal microglia in stress-induced long-term suppression of voluntary activity is unknown. Here we employ single nucleus RNA-sequencing to investigate how stress and exercise impact the biology of microglia in the striatum. We find that striatal microglia display altered activation profiles six weeks after an acute stressor. Furthermore, we show that access to a running wheel is associated with an additional and distinct microglial activation profile characterized by upregulation of genes related to complement components and phagocytosis pathways. Lastly, we find that distinct gene sets show expression changes associated with general access to a running wheel versus variation in running levels. Taken together, our results deepen our understanding of the diverse molecular states that striatal microglia assume in response to stress and exercise and suggest that microglia exhibit a broader range of functional states than previously thought.