Effects And Mechanisms Of 17? Estradiol On Propofol-induced Neuroapoptosis And Long-term Learning And Memory Deficits In Neonatal Rats

Part? The effect of 17? estradiol on propofol-induced neuroapoptosis in neonatal ratsObjective: To investigate whether 17? estradiol can attenuate propofol induced neuroapoptosis by extracellular signal-regulated kinase(ERK)signaling pathway in neonatal rats.Methods: 78 postnatal day 7 Sprague-Dawley male rat pups weighing 11 to 18 g were randomly assigned into group DMSO,F,E,P,PE and PEU,and13 per group.Group E were subcutaneously injected with 600 ?g/kg 17?estradiol and group DMSO were injected with the same volume of DMSO.Group P were intraperitoneally injected with 75 mg/kg propofol and group F were injected with the same volume of fat emulsion.Group PE was injected with 75 mg/kg propofol intraperitoneally in combination with 600 ?g/kg 17?estradiol subcutaneously.Group PEU was intraperitoneally injected with 75mg/kg propofol in combination with 600 ?g/kg 17? estradiol subcutaneously and 10 mg/kg U0126 intraperitoneally.All pups were injected once a day at regular 24 h intervals for 7 consecutive days.Throughout the anesthesia procedure,all the rat pups were placed in a temperature-controlled incubator set to an ambient temperature of 26~28? and provided with low-flow oxygen(2 L/min).Besides,respiratory and skin color were observed at the same time.Maternal separation time was no more than 5 hours until they could successfully perform the righting reflex.15 minutes after the last injection,arterial blood gas analysis were performed in 3 pups from each group to detect the levels of Pa O2.24 hours after last injection,5 pups were randomly selected from each group for immunohistochemical studies to detect cleaved-caspase 3 protein level of hippocampus respectively.Another 5 pupswere randomly selected from each group for Western blot to detect the levels of p ERK.Results:1 Pa O2 levels in each group were normal and had no significant differences(P>0.05).2 Immunohistochemical results showed that: Compared with group DMSO,no statistically significant change was found in the expression cleaved-caspase 3 protein in hippocampal in group E(P>0.05).Compared with group F,the cleaved-caspase 3 protein level in group P was increased(P<0.05).Compared with group P,cleaved-caspase 3 protein level was decreased in group PE(P<0.05).Compared with group PE,cleaved-caspase 3 protein level was increased in group PEU(P<0.05).3 Western blot results showed that: Compared with group DMSO,no statistically significant change was found in the expression p ERK protein in hippocampal in group E(P>0.05).Compared with group F,p ERK protein level was decreased in group P(P<0.05).Compared with group P,protein level of p ERK was increased in group PE(P<0.05).Compared with group PE,protein level of p ERK was decreased in group PEU(P<0.05).Conclusions:17? estradiol can attenuate propofol-induced hippocampal neuroapoptosis by activating ERK signaling pathway in neonatal rats.Part ? The effect of 17? estradiol on propofol induced long-term learning and memory deficits in neonatal ratsObjective: To investigate the neuroprotective effect of 17? estradiol on propofol induced long-term learning and memory deficits in neonatal rats.Methods: 72 postnatal day 7 Sprague-Dawley male rat pups weighing 11 to 18 g were randomly assigned into six groups: DMSO,F,E,P,PE and PEU and 12 per group.Group E were subcutaneously injected with 600 ?g/kg 17?estradiol and group DMSO were injected with the same volume of DMSO.Group P were intraperitoneally injected with 75 mg/kg propofol and group F were injected with the same volume of fat emulsion.Group PE was injected with 75 mg/kg propofol intraperitoneally in combination with 600 ?g/kg 17?estradiol subcutaneously.Group PEU was intraperitoneally injected with 75mg/kg propofol in combination with 600 ?g·?-117? estradiol subcutaneously and 10 mg/kg U0126 intraperitoneally.All pups were injected once a day at regular 24 h intervals for 7 consecutive days.Throughout the anesthesia procedure,all the rat pups were placed in a temperature-controlled incubator set to an ambient temperature of 26~28? and provided with low-flow oxygen(2 L/min).Besides,respiratory and skin color were observed at the same time.Maternal separation time was no more than 5 hours until they could successfully perform the righting reflex.15 minutes after last injection,arterial blood gas analysis were performed in 3 pups from each group to detect the levels of Pa O2.The rest 9 rats in each group were allowed to grow up till postnatal day 60 when morris water maze test was performed to evaluate their spatial learning and memory function,after which Ultraviolet colorimetry and ELISA studies were performed in 5 pups from each group to respectively detect Glu and GABA levels of hippocampal tissues and then calculate Glu/GABA ratio.Results:1 Pa O2 levels in each group were normal and had no significant differences(P>0.05).2 Morris water maze results showed that: Compared with group DMSO,no statistically significant change was found in the escape latency?time in finding the platform and ratio of time spent in platform in group E(P>0.05).The escape latency in group P was increased on the 3~5 training days,while the platform-cross times and the ratio of time spent in target quadrant were decreased in comparison with group F(P<0.05).Compare group P to group PE,rats in group PE spent less time in finding the platform on the 3~5 training days,while the ratio of time spent in target quadrant and platform-cross times were increased(P<0.05).Compared with group PE,the escape latency was increased on the 4~5 training days while the numbers of crossing over previous platform and the ratio of time spent in target quadrant were decreased in group PEU(P<0.05).3 GABA level in each group had no significant differences(P>0.05).Compared with group DMSO,no statistically significant change was found in Glu level and Glu/GABA ratio in hippocampal in group E(P>0.05).Compared with group F,Glu level and Glu/GABA ratio in group P were decreased(P<0.05).Compared with group P,Glu level and Glu/GABA ratio in group PE were increased(P<0.05).Compared with group PE,no statistically significant change was found in Glu level and Glu/GABA ratio in group PEU(P>0.05).Conclusions: 17? estradiol can attenuate propofol induced long-term learning and memory deficits probably by upregulating Glu/GABA ratio in hippocampus in neonatal rats.