eLife assessment
This important study uses cutting-edge miniature two-photon microscopy to follow the structural dynamics of microglia in the somatosensory cortex of freely-moving mice across the sleep/wake cycle. Solid evidence revealed the brain-state-dependent regulation of microglial activity, highlighting alterations in microglial morphology during REM and NREM sleep phases compared to wakefulness. Furthermore, this study provides evidence for a critical role of norepinephrine from the locus coeruleus as a modulator of microglial morphology through the β2-adrenergic receptor (b2AR). Overall, the article is an impressive technical feat to bridge a crucial gap in understanding sleep state-induced dynamics of microglia and its modulation by norepinephrine signaling.