The role of the dorsomedial periaqueductal gray glutamatergic neurons in promoting arousal under multiple general anesthetics in mice

Background: General anesthesia may involve shared neural mechanisms. The periaqueductal gray (PAG) plays a critical role in physiological, instinctive behaviors, as well as sleep-wake regulation. However, the role of the dorsomedial PAG (dmPAG) in regulating the anesthesia-awakening state remains unclear. The study aims to investigate the role of dmPAG glutamatergic neurons in promoting arousal under multiple general anesthetics. Methods: Multiple general anesthetics, including sevoflurane, propofol, ketamine, and dexmedetomidine, were administered to mice of both sexes. Calcium imaging was employed to monitor activity changes in glutamatergic neurons within the dmPAG during anesthesia and arousal. Optogenetic and chemogenetic approaches were used to manipulate neuronal activity and evaluate their effects on anesthesia induction, maintenance, and recovery. Additionally, electroencephalogram (EEG) recordings were analyzed to assess alterations in spectral power and the burst-suppression ratio under anesthesia. Results: Glutamatergic neuronal activity in the dmPAG was suppressed during sevoflurane anesthesia but increased during wakefulness, with similar patterns observed for all intravenous anesthetics tested. Optogenetic activation of dmPAG glutamatergic neurons significantly prolonged anesthesia induction time (GFP vs. ChR2, 218.8 ± 50.83 s vs. 372.5 ± 40.18 ;s, P <0.001) and shortened emergence time (GFP vs. ChR2, 230.8 ± 40.44 s vs. 135 ± 19.82 s, P <0.001) under sevoflurane anesthesia. EEG changes characteristic of wakefulness was observed during maintained anesthesia, with the burst suppression ratio decreasing (GFP vs. ChR2: 50.08 ± 8.21% vs. 2.15 ± 3.38%, P <0.001). Chemogenetic activation produced similar effects, while chemogenetic inhibition potentiated the anesthetic effects of all tested anesthetics. Conclusions: The findings suggest that glutamatergic neurons in the dmPAG may act as a common neural substrate for multiple anesthetic agents, playing a critical role in both the loss and recovery of consciousness.