Activation of CaMKII+ neurons in the paramedian raphe nucleus promotes general anesthesia in male mice

General anesthesia (GA) is an essential clinical and surgical adjunct, widely recognized as the result of coordinated networks among numerous brain regions. Anesthetic drugs with different characteristics are associated with distinct networks of brain regions involved in anesthesia. Ciprofol, a novel intravenous anesthetic derived from structural modifications of propofol, has shown promise in clinical applications. However, the specific neuronal circuits and brain regions mediating their actions may differ. Moreover, the core brain regions that mediate the common anesthetic effects of these drugs remain unclear. In this research, we identified a central ensemble of brainstem neurons within the paramedian raphe nucleus (PMnR) using c-Fos staining in mice subjected to GA induced by continuous intravenous infusion of ciprofol and propofol. This neuronal population, primarily composed of CaMKIIa and Gad1-expressing cells, demonstrated consistent activation in reaction to ciprofol. Optogenetic activation of PMnR^CaMKIIa neurons induced a GA state under ciprofol pre-administration, while sole activation of PMnR^CaMKIIa neurons induced a motionless state in mice. In addition, conditional inhibition of these neurons resulted in resistance to GA. In summary, we highlight the PMnR as a brain target for ciprofol and propofol. Furthermore, CaMKIIa⁺ neurons in the PMnR emerge as active promoters of the anesthesia process, shedding light on a previously unrecognized key player in the intricate neural network orchestrating GA.

Chemogenetic; Ciprofol; Electroencephalogram; General anesthesia; In situ sequencing; Optogenetics; Paramedian raphe nucleus; Propofol.