Esketamine increases neurotransmitter releases but simplifies neurotransmitter networks in mouse prefrontal cortex

General anesthesia induces a profound but reversible unconscious state, which is accompanied by changes in various neurotransmitters in the cortex. Unlike the "brain silencing" effect of γ-aminobutyric acid (GABA) receptor potentiator anesthesia, ketamine anesthesia leads the brain to a paradoxical active state with higher cortical activity, which is manifested as dissociative anesthesia. However, how the overall neurotransmitter network evolves across conscious states after ketamine administration remains unclear. Using in vivo microdialysis, high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, and electroencephalogram (EEG) recording technique, we continuously measured the concentrations of six neurotransmitters and the EEG signals during anesthesia with esketamine, an S-enantiomer of ketamine racemate. We found that there was an increase in the release of five cortical neurotransmitters after the administration of esketamine. The correlation of cortical neurotransmitters was dynamically simplified along with behavioral changes until full recovery after anesthesia. The esketamine-increased gamma oscillation power was positively correlated only with the concentration of 5-hydroxytryptamine (5-HT) in the medial prefrontal cortex. This study suggests that the transformation of the neurotransmitter network rather than the concentrations of neurotransmitters could be more indicative of the consciousness shift during esketamine anesthesia.NEW & NOTEWORTHY In this study, we found that esketamine significantly increased the cortical concentration of multiple neurotransmitters in mice. However, esketamine dynamically simplified the overall network of cortical neurotransmitters at different behavioral states during the perianesthesia period. The concentration of 5-HT in the medial prefrontal cortex (mPFC) was highly correlated with the esketamine-increased gamma oscillation. These findings suggested that the transformation of the neurotransmitter network rather than the concentrations of neurotransmitters could be more indicative of the consciousness shift during esketamine anesthesia.