Multiple exposures to sevoflurane during the neonatal period impair hippocampus development and cognitive function in young mice

Sevoflurane is a commonly used anesthesia for infants and young children. Sevoflurane has potential neurotoxicity in immature brains; however, its specific mechanism has not been fully elucidated. Therefore, we used an established sevoflurane anesthesia model and evaluated hippocampal synaptic function using transcriptome sequencing, biochemical analyses, and animal behavior to investigate the effect of multiple neonatal sevoflurane exposures on the hippocampus in mice. C57BL/6J mice were randomly divided into sevoflurane and control groups. All experimental conditions were identical in the two groups except for the anesthetization procedure. Mice in the sevoflurane group were anesthetized with 2.5% sevoflurane for 2 h daily for 3 consecutive days (postnatal days 6-8). Mice in the control group did not receive sevoflurane anesthesia. During anesthesia, mice were administered 50% oxygen, and the respiratory rate and skin color were monitored. On day 3 of modeling, half of the mice were randomly selected to undergo harvesting of the hippocampus. RNA sequencing (RNA-seq) of RNA extracted from the hippocampus identified 736 differentially expressed genes (DEGs), including 433 upregulated and 303 downregulated DEGs, after multiple sevoflurane exposures. Gene ontology term enrichment analysis results suggested that sevoflurane exposure altered the expression of neurodevelopment-related genes in neonatal mice. Several enriched biological processes involved in brain development (axon/forebrain development) and adenosine monophosphate-activated protein kinase signaling pathways were highlighted. Comparison with RNA-seq database information showed that DEGs of the neonatal hippocampus after multiple exposures to sevoflurane were specific to neonatal mice. Furthermore, Morris water maze testing confirmed that sevoflurane anesthesia induced learning and memory impairments in young mice. Additionally, Western blot and immunofluorescence analyses showed that sevoflurane treatment decreased synaptic protein levels, such as postsynaptic density protein 95, synaptosomal-associated protein, 25 kDa, and B-cell lymphoma 2-associated athanogene 3, in the hippocampus, which induced synaptic dysfunction, resulting in impaired nervous system development in young mice.