Immunostaining and fiber photometry were used to assess the neuronal activities. Electroencephalography spectra and burst-suppression ratio (BSR) were used to measure anesthetic depth and loss or recovery of righting reflex to indicate the induction or emergence time of general anesthesia. Regulation of serotonergic system was achieved through optogenetic, chemogenetic, or pharmacological methods.
We found that both Fos expression and calcium activity were significantly decreased during general anesthesia. Activation of 5-HT neurons in the dorsal raphe nucleus (DRN) decreased the depth of anesthesia and facilitated the emergence from anesthesia, and inhibition deepened the anesthesia and prolonged the emergence time. Furthermore, agonism or antagonism of 5-HT 1A or 2C receptors mimicked the effect of manipulating DRN serotonergic neurons.
Our results demonstrate that 5-HT neurons in the DRN play a regulative role of general anesthesia, and activation of serotonergic neurons could facilitate emergence from general anesthesia partly through 5-HT 1A and 2C receptors.