The Effect And Mechanism Of Propofol Anesthesia On Spatial Memory In Infant Rats Under Hypoxic Conditions

Objective:To evaluate the effect of propofol on spatial memory in infant rats under hypoxic conditions.Methods:Forty-eight seven-day old SD rats were randomly divided into 6 groups(n=8): propofol+18% oxygen (propofol-hypoxia, PH), propofol+air (propofol-air,PA), propofol+100% oxygen (propofol-oxygen, PO), control group: intralipid +18% oxygen (CH), intralipid + air (CA), intralipid +100%oxygen (CO). After intraperitoneal injection of 50 mg/kg propofol or identical volume intralipid, the rats were exposed in 18% oxygen, air or 100% oxygen until recovery of the righting reflex, 1 time/d, 7 d continuous. SaO₂(%) and respiratory rate(RR) were monitored throughout the procedures. Two weeks after treatment, animals were challenged with Morris water maze test.Results:Compared with CO group, RR decreased and the average time of escape latency was significantly longer on the first and second day in PO group(P <0.05).Compared with CA group,RR and SaO₂ significantly decreased, the average time of escape latency was longer, the number of platform location crossing was less in PA group (P < 0.05). Compared with CH group, RR and SaO₂ significantly decreased, the average time of escape latency was longer,the number of platform location crossing was significantly less in PH group(P <0.05). Compared with PO group, SaO₂ significantly decreased, the average time of escape latency was longer,the number of platform location crossing was less in PA group and PH group(P<0.05).These were no significant differences in CO group, CA group and CH group(P>0.05).Conclusion:Propofol anesthesia per se induced short-term impairment of postanesthesia cognitive performance, but propofol in combination with hypoxia lastingly impair cognitive function in newborn rats.Objective: To evaluate the effect of propofol on apoptosis in infant rat hippocampus under hypoxic conditions.Methods: The same group and treatment as part one. SaO2 (%) and RR were monitored throughout the procedures. After 24 h, TUNEL staining, the expression of caspase-3 and ultrastructural changes in the hippocampus were assessed.Results: Compared with CO group, RR significantly decreased in PO group(P <0.05). Compared with CA group , RR and SaO₂ significantly decreased, apoptotic index increased, expression of caspase-3 significantly enhanced in PA group (P < 0.05). Compared with CH group,RR and SaO₂ decreased, apoptotic index increased,expression of caspase-3 enhanced in PH group(P <0.05). Compared with PO group, SaO₂ decreased, apoptotic index increased,expression of caspase-3 enhanced in PA group and PH group(P <0.05).These were no significant differences in CO group, CA group and CH group(P>0.05). Transmission electron microscope found neuronal shrinkage, condensed chromatin, cellular pykno-structure, cell membrane incisures, karyopyknosis, nuclear membrane incisures in PA group and PH group and these were no significant differences in CO group, CA group, CH group and PO group.Conclusion: Propofol anesthesia per se didn't induce significant hippocampal neuronal apoptosis, but propofol anesthesia induced significant hippocampal neuronal apoptosis under hypoxic conditions. Objective: To evaluate the effects of propofol on long term potentiation in infant rat hippocampal slices under hypoxic conditions. Methods:The same group and treatment as part one. SaO₂ (%) and RR were monitored throughout the procedures. After 24 h, hippocampus was removed and sliced. fEPSP and the success rate of LTP were recorded.Results: Compared with CO group, RR significantly decreased, fEPSP and the success rate of LTP reduced in PO group(P <0.05). Compared with CA group,RR and SaO₂ decreased, fEPSP reduced, the success rate of LTP reduced in PA group (P < 0.05). Compared with CH group,RR and SaO₂ decreased, fEPSP and the success rate of LTP reduced in PH group(P <0.05). Compared with PO group, SaO₂ decreased, fEPSP and the success rate of LTP reduced in PA group and PH group(P <0.05). These were no significant differences in CO group, CA group and CH group (P>0.05).Conclusion: Propofol anesthesia per se reduced significantly fEPSP and the success rate of LTP in infant rats, more significantly inhibited the induction of LTP under hypoxic conditions. Objective:To evaluate the effects of propofol on Ca²⁺ and CaMKâ…¡protein in infant rat hippocampus under hypoxic conditions.Methods:The same group and treatment as part one. SaO₂ (%) and RR were monitored throughout the procedures. After 24 h, hippocampus was removed. Ca²⁺ and CaMKâ…¡protein in infant rat hippocampus were monitored by confocal laser microscope and Western blot.Results:Compared with CO group, RR significantly decreased, Ca²⁺ increased and CaMKâ…¡expression reduced in hippocampus in PO group(P<0.05).Compared with CA group,RR and SaO₂ decreased, Ca²⁺ increased and CaMKâ…¡expression reduced in hippocampus in PA group (P < 0.05). Compared with CH group,RR and SaO₂ decreased, Ca²⁺ in hippocampus increased and CaMKâ…¡expression reduced in PH group(P <0.05). Compared with PO group,SaO₂ decreased, Ca²⁺ in hippocampus significantly increased and CaMKâ…¡expression significantly reduced in PA group and PH group(P <0.05). These were no significant differences in CO group, CA group and CH group (P>0.05).Conclusion:Propofol anesthesia per se induced Ca²⁺ significantly increase and CaMKâ…¡expression significantly decrease in infant rat hippocampus, Ca²⁺ more significantly increased and CaMKâ…¡more significantly decreased under hypoxic conditions.