Effects Of The General Anesthetics On The Developing Nervous System And The Underlying Neural Neurobiological Mechanism

BackgroundRecently,the influence of general anesthesia drugs on the developing brain has become a research hotspot.Studies have shown that single or combined application of general anaesthetics can cause the neuronal apoptosis in the developing brain area of animals.In addition to the temporary inhibition of central nervous system function and neural transduction,it can also cause long-term cognitive emotion,learning and memory and other behavioral changes.Cognitive and behavioral disorders are more likely to occur after repeated and prolonged exposure to general anesthesia before age 3,and the risk of occurrence is directly related to the frequency of anesthesia,duration of exposure,and dose.Previous studies focus on the molecular and biochemical effects of specific anaesthetic drug to study the neurotoxicity,which lacks the systematic study of the effect to the neural circuits.In this study,we have demonstrated that ketamine and isoflurane induce emotional disorder and cognitive disorder in developing mice which is conducted through behavioral test,physiological test,immunohistochemistry study,in situ hybridization test,chemogenetic test.Through the expression of the neural-activity-dependent protein c-Fos,in vivo calcium fluorescent study,and Neurologger brain electrophysiological analysis,we have also found that dexmedetomidine protects the animals from the isoflurane induced cognitive disorder.BNST,dCA1,ZI might be involved in the protection effect of DEX to the isoflurane induced cognitive disorder.We assume that,the developing neural circuit is involved during the ketamine and isoflulrane induced damage and DEX induced protection process.The synaptic connection may have changed during this process.ObjectiveThe objectives of this study is to identify the damaging effect of ketamine and isoflurane as anaesthetics to the developing nervous system and the clinical protection effect of Dexmedetomidine in this process.The circuitry nervous mechanism involving BNST,dCA1,ZI during the anaesthetics induce developing nervous injury will also be studied.MethodsThe mice anxiety level and cognition are studied by animal behavior tests including open field test,elevated plus maze test and fear conditioning test.The animal physiological conditions are assessed by biochemistry tests.The neuron C-Fos expression is assessed by immunohistofluorescent study.The intracellular GAD 1/2 and vGlut2 mRNA level is assessed by in situ hybridization.The real-time brain area activation is assessed by in vivo calcium fluorescent study.Neurologger is applied to study the electrophysiological connection between different neurons.Results1、Exposure to ketamine during the metaphase of pregnancy would induce anxiety behavior in F1 offspring mice which is indicated by shorter time in the central area of open field test and open arm of elevated plus maze test.2、The BNST is associated with the anxiety behavior in F1 spring which is presented by increased expression of cFos in the neurons.Chemogenetic inhibition of BNST neuron activity reversed the anxiety behavior of the F1 off spring mice.3、P7 mice received isoflurane were induced cognitive disorder in 56-day,which is presented by decrease ’freezing time’ in conditional fear test.Dexmedetomidine protected the animal from isoflurane induced cognitive disorder.4、Isoflurane induced decrease of serum glucocorticoid in developing mice which is reversed by Dexmedetomidine.5、From the c-Fos mapping and in vivo GCaMP fluorescent study,it was found that dCAl and ZI are important nuclei during the Dexmedetomidine protection of cognitive function in developing mice after exposure to isoflurane.6、The dCAl and ZI function during the Dexmedetomidine protection of cognitive function in developing mice after exposure to isoflurane was recorded by Neurologger.Comparing to the ISO group,the Beta wave and Gamma wave in dCAl is lower while the Gamma wave in ZI is lower in the ISO+DEX group.Conclusion1、Exposure to Ketamine may induce anxiety behavior in offspring mice which is conducted through BNST.2、Dexmedetomidine protects the isoflurane induced brain cognitive function disorder,which is conducted through dCAl and ZI while the neuron connection is altered during this process.