The Effects Of Sevoflurane Exposure At Different Concentrations During Late Pregnancy On Offspring Rat Neurobehavior And Its Mechanism

Objective:In this study,rats in the third trimester of pregnancy were anesthetized with different concentrations of sevoflurane commonly used in clinic.Behavioral experiments were used to observe the changes of early postnatal nerve reflex and long-term cognitive function in offspring rats.To investigate the effect of sevoflurane on brain development of offspring rats and its potential mechanism.Methods:On gestational day 17,24 Sprague-Dawley（SD）rats were randomly divided into control group,2% sevoflurane group and 3% sevoflurane group.All rats were fed until natural delivery,and the brain tissues of offspring on postnatal day 1（P1）,day 8（P8）and day 33（P33）were taken.Hematoxylin eosin（HE）staining was used to observe the pathological changes of hippocampus in offspring rats;The expression of ionized calcium binding adaptor Molecule 1（IBA1）and phospho-nuclear factor-κB p65（P-P65）in the rat hippocampus was detected by immunohistochemistry.Western blotting was used to evaluate the expression of pro-inflammatory cytokines interleukin-6（IL-6）,tumor nectosis factor-α（TNF-α）and NF-κB pathway protein（P65/P-P65）in rat hippocampus.Cliff avoidance was conducted for P8-P14 to detect motor and sensory function in early development,and morris water maze test was conducted for P28-P33 to detect long-term cognitive ability.This experiment was completely randomized design.One-way analysis of variance was used for comparison between groups.Repeated measures analysis of variance and post-hoc Bonferroni test were used in the Morris water maze positioning navigation experiment and cliff avoidance.Results:The lip color and respiratory amplitude of pregnant rats were normal during sevoflurane anesthesia in the third trimester of pregnancy.There was no death in the offspring of pregnant rats in each group.There was a non-significant difference in cliff aversion test of the offsprings between control group and 2% sevoflurane group（P>0.05）.The time of cliff aversion reaction of offspring rats in the 3% sevoflurane group was longer than that in the control group at P8-P11（P<0.05）,but there was no statistically significant difference between the two groups at P12-P14（P>0.05）.Morris water maze showed that there was no significant difference in the five-day escape latency among the three groups（F=0.310,P=0.736）.At the same time,no statistically significance was found in the platform crossing times between the three groups（F=0.448,P=0.643）.HE staining showed that the neurons in the hippocampus of the offspring of the control group and 2% sevoflurane group were arranged orderly,with rich cytoplasm,round nucleus and clear nucleolus at three time points.Compared with the control group,the 3%sevoflurane group had different degrees of injury at P1 and P8.At P1,nuclear pyknosis,tissue edema and loose cell arrangement occurred in the hippocampus of the offspring in the3% sevoflurane group.At P8,the cells in hippocampus of 3% sevoflurane group were loosely arranged.At P33,no obvious pathological damage was found in the hippocampus of3% sevoflurane group.Immunohistochemical results showed that compared with the control group,the expression of IBA1 and P-P65 in hippocampus of the 3% sevoflurane group was increased at both observation time points P1 and P8.The expression of IBA1 and P-P65 in hippocampus of 3% sevoflurane group was not significantly different from that of control group at P33.There was no significant difference in the expression of IBA1 and P-P65 in hippocampus of offspring in 2% sevoflurane group at three time points compared with the control group.Western blotting showed that the expression levels of IL-6,TNF-α and P-P65/P65 in the hippocampus of the 2% sevoflurane group were not significantly different from those of the control group at three time points（P>0.05）.The levels of IL-6,TNF-α and P-P65/P65 protein in the hippocampus of 3% sevoflurane group at P1 and P8 were significantly higher than those in the control group（P<0.05）.At P33,the levels of IL-6,TNF-α and P-P65/P65 protein in hippocampus of 3% sevoflurane group showed no significant difference compared with control group（P>0.05）.Conclusion:The neurotoxicity of maternal exposure to high concentration（3%）sevoflurane in the third trimester of pregnancy to the brain development of offspring rat was greater than that of low concentration（2%）sevoflurane.High concentrations of sevoflurane activates the NF-κB pathway to induce neuroinflammation,leads to early motor sensory dysfunction in offspring rat,and does not affect long-term cognitive function.