Ketamine's Brain Spatial Distribution and Metabolic Effects in a Mouse Model of Anxiety: Insight into In Situ Mass Spectrometry Imaging and Metabolomics Methods

Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, exhibits both therapeutic potential and abuse liability. However, the spatial distribution of ketamine across brain regions remains poorly characterized. Meanwhile, elucidating the mechanism underlying ketamine-induced psychiatric disorders through the investigation of metabolite alterations in the specific brain regions targeted by ketamine is of crucial significance. This study investigated the neurochemical effects of chronic ketamine administration in C57BL/6 mice using in situ mass spectrometry imaging (MSI) and metabolomics. Mice treated with ketamine (30   mg/kg daily for 15 days) exhibited increased anxiety-like behaviors without cognitive deficits. MSI revealed ketamine accumulation in the cerebral cortex, midbrain, and cerebellum, while the key neurotransmitter γ-aminobutyric acid (GABA) distribution shifted toward thalamic and striatum regions. The prefrontal cortex and cerebellum were selected as targeted brain regions for metabolomics analysis based on the MSI results. In metabolomics results, 73 and 134 differential metabolites in the prefrontal cortex and cerebellum were identified, respectively, predominantly linked to Alanine, aspartate, and glutamate metabolism, Estrogen signaling pathway, and GABAergic synapse pathways. This study integrated behavioral assessments, in situ MSI, and metabolomics to visually resolve and multidimensionally correlate ketamine's spatial distribution in the brain with region-specific metabolic changes in a ketamine-induced anxiety model. The findings reveal distinct neurochemical disruptions across brain regions and offer a groundwork for further elucidating the mechanisms of ketamine-related anxiety.