The Somatostatin Pathway Projected from the Basal Forebrain to the Lateral Habenula Promotes Isoflurane Anesthesia Recovery

The basal forebrain (BF) acts as a pivotal relay station in the transmission of arousal signals, projecting to both cortical and subcortical structures. Among its downstream targets is the lateral habenula (LHb), which recent research has implicated in the modulation of sleep rhythms and in mediating the loss of consciousness associated with anesthetic agents. In our study, we utilized optogenetic manipulation to selectively modulate the BF^VGluT2/SOM neuron projection pathway to the LHb, thereby examining its impact on behavioral and electroencephalographic responses to isoflurane anesthesia. Our results demonstrated that in healthy adult male mice, the activation of the BF^SOM→LHb projection pathway significantly prolonged the induction time of anesthesia and shortened recovery time, consequently diminishing the anesthetic potency of isoflurane and reducing EEG δ power. In contrast, the inhibition of this pathway yielded the inverse effects. Notably, modulation of the BF^VGluT2→LHb projection pathway did not significantly affect the induction or recovery times of isoflurane anesthesia. Employing optogenetics in conjunction with calcium signal recording, we elucidated that the arousing effect of the BF^SOM→LHb pathway is attributable to the enhanced inhibitory action of BF^SOM neurons on LHb^Glu neurons. This discovery sheds new light on the neural circuits involved in the loss and recovery of consciousness induced by anesthetic drugs, potentially informing future therapeutic strategies.