A dopaminergic projection from the ventral tegmental area to the dorsal raphe nucleus critically regulates propofol anesthesia in mice

General anesthesia induces a reversible loss of consciousness, yet the precise neural circuits mediating this state transition remain incompletely understood. The ventral tegmental area (VTA) dopaminergic (DA) neurons and the dorsal raphe nucleus (DRN) serotonergic (5-HT) neurons are key components of the ascending arousal system. This study investigated the existence and functional role of VTADA→DRN5-HT circuit in regulating propofol anesthesia. Using virus-mediated neural circuit tracing in DAT-Cre and TPH2-CreER transgenic mice, we demonstrated an anatomically connected circuit appositions between VTADA axon terminals and DRN5-HT neurons. In vivo fiber photometry revealed that the activity of both presynaptic VTADA terminals in the DRN and postsynaptic DRN5-HT neurons was significantly suppressed under propofol anesthesia. Chemogenetic activation of either VTADA or DRN5-HT neurons facilitated emergence from propofol anesthesia, whereas their inhibition prolonged the duration of anesthesia. Optogenetic activation of VTADA terminals within the DRN rapidly induced behavioral and electroencephalographic (EEG) arousal from stable propofol anesthesia. Crucially, this pro-arousal effect was abolished by chemogenetic inhibition of DRN5-HT neurons, indicating a functional hierarchy. These findings identify a putative direct pathway VTADA→DRN5-HT circuit that bidirectionally regulates propofol anesthesia, providing a novel neural substrate for conscious state control and a potential target for therapeutic interventions.