| BackgroundAs a commonly used intravenous anesthetic in clinical practice,propofol has attracted great attention in the safety of infants and young children.There is a large body of evidence of propofol indicate that it can cause brain neuronal damage during development,while the conclusion on the impact of oligodendrocytes caused by it is still deficient.Oligodendrocytes are myelin cells in the central nervous system that provide insulation for axons and ensure fast and effective conduction of action potentials.In addition,it can provide nutrition and neuronal axon support for the survival of neuronal axons.Previous studies have shown that propofol embryonic or neonatal exposure can increase oligodendrocyte apoptosis,but the dose-related effects,myelin structure changes and whether it is a permanent injury have not been reportedObjectiveTo investigate the effects of different doses of propofol on the synthesis of Myelin Basic Protein(MBP)and brain myelination formation in neonatal SD rats oligodendrocyte,and to observe the presence and duration of oligodendrocyte injury and to observe whether the ultrastructure of myelin has changed.Materials and Methods1.Grouping of experimental animalsTwenty-two SD pregnant rats were spontaneously delivered,and 229 of them were randomly divided into 5 groups:control group(n=55),vehicle of fat emulsion group(n=26),propofol 25(n=45),50(n=45)and 100 mg/kg group(n=58).On the 7th day after birth(P7),after calculating the dosage,single intraperitoneal injection of equal volume was administrated as 0.4ml/rat.Those with insufficient volume were supplemented with normal saline.An equal volume of normal saline and a medium long chain fat emulsion were administered to the Control group and the Vehicle group,respectively.Samples were taken at 8h,24h(P8),3d(P10),7d(P14),and 14d(P21)after administration.2.Detection of mbp mRNA,caspase-3 mRNA and MBP proteinBrain tissue was taken at different time points after propofol exposure,and the expression of mbp,caspase-3 mRNA and MBP protein were detected by qPCR and WB.3.Oligodendrocytes apoptosis,proliferation and myelinationParaffin sections of brain tissue were prepared,TUNEL staining was used to detect oligodendrocytes apoptosis;NG2/PCNA staining was used to detect oligodendrocytes precursor cell proliferation;MBP staining was used to detect myelination.4.Observation of myelin sheath by transmission electron microscopeUltrathin sections were prepared and the changes in myelin ultrastructure were observed under a transmission electron microscope.5.Statistical analysisMeasurement data were showed in the way of mean±standard deviattion.SPSS 20.0 was used for independent sample t test and One-way ANOVA and multiple comparison between pairs using LSD method.P<0.05 was considered statistically significant.Results1.The expression of mbp mRNA and protein were down-regulated at 8h,24h and 3d(P10)after exposure(P<0.05).There was no difference between 7d(P14)and 14d(P21)compared with the control group(P>0.05).).2.The expression of caspase-3 mRNA was up-regulated at 8h and 24h after exposure and there was a significant difference between each two groups(P<0.05).Apoptosis of oligodendrocytes increased at 24h and there was significant difference between each groups,and proliferation of progenitor cells decreased in 50 and 100mg/kg groups.(P<0.05).3.Myelin formation in corpus callosum and internal capsule decreased in 50 and 100 mg/kg groups in 24 hours and 3 days after exposure.There has a significant decrease on myelination in the corpus callosum and internal capsule at 24h and 3d(P10)with 50 and 100mg/kg after exposure(P<0.05),and there was no difference between 7d(P14)and 14d(P21)compared with the control group(P>0.05).4.The changes of myelin sheath in the corpus callosum were increased in 100mg/kg group 3 days after exposure(P<0.05);There was no difference at 7d(P14)and 14d(P21)compared with the control group(P>0.05).Conclusion1.Single propofol exposure in neonatal SD rats induces an increase in oligodendrocyte apoptosis and a decrease in OPCs proliferation with a dose-dependent manner during the acute phase,which leads to the decrease of MBP gene and protein expression.2.Single propofol exposure in neonatal SD rats affects the formation of myelin sheath in the corpus callosum and the internal capsule in varying degrees.3.Single propofol exposure in neonatal SD rats can induces changes in layer structure of myelin under electron microscope.4.The effects of single propofol exposure on oligodendrocytes in neonatal SD rats are non-permanent and can return to normal before the end of lactation. |
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