Astrocytic IP₃/Ca²⁺ Signaling Modulates Theta Rhythm and REM Sleep

Rapid eye movement (REM) sleep onset is triggered by disinhibition of cholinergic neurons in the pons. During REM sleep, the brain exhibits prominent activity in the 5-8 Hz (theta) frequency range. How REM sleep onset and theta waves are regulated is poorly understood. Astrocytes, a non-neuronal cell type in the brain, respond to cholinergic signals by elevating their intracellular Ca²⁺ concentration. The goal of this study was to assess the sleep architecture of mice with attenuated IP₃ mediated Ca²⁺ signaling in astrocytes. Vigilance states and cortical electroencephalograph power were measured in wild type mice and mice with attenuated IP₃/Ca²⁺ signaling. Attenuating IP₃/Ca²⁺ signaling specifically in astrocytes caused mice to spend more time in REM sleep and enter this state more frequently during their inactive phase. These mice also exhibited greater power in the theta frequency range. These data suggest a role for astrocytic IP₃/Ca²⁺ signaling in modulating REM sleep and the associated physiological state of the cortex.