RESUMO
[ABSTRACT]AIM:Toinvestigatetheeffectofsevoflurane(Sevo)onthedendriticdevelopmentinprefrontal cortex ( PFC) of neonatal rats and the role of cyclin dependent kinase 5 ( Cdk5 )-collapsin response mediator protein ( CRMP) pathway in it.METHODS:Eighty-eight postnatal day 7 Sprague Dawley ( SD) rats were randomly divided into 4 groups (n=22):Air+NS group, Air+roscovitine (Ros) group, Sevo+NS group and Sevo+Ros group.The rats in Air+NS group and Air+Ros group were exposed to the air for 4 h, while the rats in the other 2 groups were exposed to 2.8%sevoflurane for 4 h.The rats received intraperitoneal injection of 150μL normal saline 15 min before exposure in the Air+NS group and Sevo+NS group, while the rats in the Air+Ros group and Sevo+Ros group received intraperitoneal injection of 150μL roscovitine ( in DMSO solution, 10 mg/kg) 15 min before exposure.At the end of exposure, the corti-ces of the rat brain were collected and the protein levels of P35, P25, Cdk5, CRMP1, CRMP2, CRMP4 and p-CRMP2 Ser522 in PFC were detected by Western blot.On the postnatal day 30, the rat brains were sectioned for Golgi-Cox staining and morphological analysis of dendrites in the PFC neurons.Open-field test and contextual fear conditioning test were per-formed on postnatal days 25~27 and 31~32, respectively.RESULTS:Compared with Air+NS group, the expression of P35 in the Sevo+NS group was significantly decreased, and the expression of P25 was dramatically increased (P<0.05), whereas roscovitine partly reversed the changes above induced by sevoflurane (P<0.05).The expression of Cdk5 was not significantly different among all groups.Compared with the Air+NS group, the expression of CRMP1, 2, and 4 in the Se-vo+NS group were decreased, and the protein level of p-CRMP2 Ser522/CRMP2 was increased ( P<0.05 ) , whereas roscovitine partly reversed the changes above induced by sevoflurane (P<0.05), except for the expression of CRMP2. Compared with Air+NS group, the total dendrite length, secondary dendritic length and interactions on 60 and 80 μm shells in the Sevo+NS group were decreased (P<0.01), whereas roscovitine partly reversed the changes above induced by sevoflurane (P<0.05).Compared with Air+NS group, the percentage of freezing time in the Sevo+NS group was de-creased (P<0.01), whereas roscovitine partly reversed the changes induced by sevoflurane (P<0.05).No significant difference among groups in the open-field test was observed.CONCLUSION:Sevoflurane exposure disturbed dendritic de-velopment of neurons in PFC, learning and memory ability of neonatal rats, which may be mediated by Cdk5-CRMP path-way.
RESUMO
Objective To investigate the effects of isoflurane and sevoflurane at the equivalent depth of subanesthesia on neuronal proliferation and phosphorylation of extraceullar signal-regulated kinase 1/2 (ERK1/2)protein in the hippocampi of neonatal rats.Methods Seventy-two neonatal rats at postnatal day 7 were involved in this study and they were assigned randomly into isoflurane group (Iso group),sevoflurane group (Sev group) and control group (Con group).The rats in I group,S group or C group were separately exposed to 0.75％ isoflurane or 1.2％ sevoflurane (equivalent to 0.3 MAC for neonatal rats) or air for 6 h.Some rats in each group were injected intraperitoneally BrdU 100 mg/kg immediately (D0) (n =6) or 3 days after exposure (D3) (n =6),and their brains were perfusion and embedded by paraffin 24 h after BrdU injection.BrdU positive expressions in the in dentate gyrus (DG) area of hippocampus were detected by IHC staining.Besides,the fresh hippocampi of some rats each group were dissected at the end of anesthesia,caspase-3 and phospho-ERK1/2,ERK1/2 proteins expression were detected by Western blot (n =6).The other rats in each group were used to measure changes of pH and blood glucose (n =6).One way ANOVA test was used for data analysis among groups.Results BrdU-positive cells had no significant difference among group IsoD0 ((1332.43 ± 192.70)/mm2),group SevD0 ((1207.33 ±139.50)/mm2),and group ConDO ((1362.40 ± 227.90)/mm2) at D0,while which had significantly decreased by 32.6％ (P＜ 0.05) in group IsoD3 ((604.56 ± 65.77)/mm2) when compared with those in group ConD3 ((896.90 ± 78.77)/mm2) at D3.There was no significant difference between groups of SevD3 ((808.73 ± 41.27)/mm2) and ConD3.The expression of caspase-3 protein was increased by 195％ (P＜ 0.01) in Iso group while which only increased by 74％ (P ＜ 0.05) in Sev group when compared with Con group.The expression of P44 and P42 of phospho-ERK1/2 protein in the hippocami decreased by 53％ (P ＜ 0.01) and 47％ (P ＜ 0.01))seperately in Iso group when compared with Con group,while there were no significant differences between Sev group and Con group.Conclusion 0.3 MAC isoflurane,not sevoflurane inhibits neuronal proliferation in DG of hippocampi in the neonatal rats.Inhibiting ERK1/2 phosphorylation may involve in the mechanisms of that isoflurane inhibits neuronal proliferation.
