Sevoflurane is the most commonly used volatile anesthetic during pregnancy.The viability of neural stem cells directly affects the development of the brain.However,it is unknown whether the use of sevoflurane during the second trimester affects the survival of fetal neural stem cells.Therefore,in this study,we investigated whether exposure to sevoflurane in mid-gestation induces apoptosis of neural stem cells and behavioral abnormalities.On gestational day 14,pregnant rats were anesthetized with 2％ or 3.5％ sevoflurane for 2 hours.The offspring were weaned at 28 days and subjected to the Morris water maze test.The brains were harvested to examine neural stem cell apoptosis by immunofluorescence and to measure Nestin and SOX-2 levels by west blot assay at 6,24 and 48 hours after anesthesia as well as on postnatal day (P) 0,14 and 28.Vascular endothelial growth factor (VEGF) and phosphoinositide 3-kinase (PI3K)/AKT pathway protein levels in fetal brain at 6 hours after anesthesia were assessed by west blot assay.Exposure to high-concentration (3.5％) sevoflurane during mid-gestation increased escape latency and path length to the platform,and it reduced the average duration spent in the target quadrant and platform crossing times.At 6,24 and 48 hours after anesthesia and at P0,P14 and P28,the percentage of Nestin/terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells was increased,but Nestin and SOX-2 protein levels were decreased in the hippocampus of the offspring.At 6 hours after anesthesia,VEGF,PI3K and phospho-AKT (p-AKT) levels were decreased in the fetal brain.These changes were not observed in animals given low-concentration (2％) sevoflurane exposure.Together,our findings indicate that exposure to a high concentration of sevoflurane (3.5％) in mid-gestation decreases VEGF,PI3K and p-AKT protein levels and induces neural stem cell apoptosis,thereby causing leing and memory dysfunction in the offspring.