Effects of isoflurane postconditioning on long-term cognitive function of neonatal rats with hypoxic-ischemic brain injury / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the effects of isoflurane postconditioning on long-term cognitive function of neonatal rats with hypoxic-ischemic brain injury (HIBI).Methods Sixty 7-day-old Sprague-Dawley rats,weighing 12-16 g,were randomly divided into 4 groups (n =15 each) using a random number table:sham operation group (group Ⅰ),isoflurane postconditioning group (group Ⅱ),cerebral hypoxia-ischemia group (group Ⅲ),and isoflurane postconditioning after cerebral hypoxia-ischemia group (group Ⅳ).Brain ischemia was induced by permanent ligation of the left common carotid artery followed by inhalation of 8 ％ O2-92 ％ N2 for 2 h at 37 ℃ in Ⅲ and Ⅳ groups.In Ⅰ and Ⅱ groups,the left common carotid artery was only isolated but not ligated.The rats inhaled 1.5％ isoflurane in 30％ O2-70％ N2 for 30 min starting from 2 h of hypoxia in Ⅱ and Ⅳ groups.The rats were exposed to 30％ O2-70％ N2 for 30 min in Ⅰ and Ⅲ groups.Morris water maze test was carried out at 30-35 days after HIBI.The escape latency,swimming speed,swimming distance,the number of times the animals crossing the platform quadrant,the percentage of time spent in the platform quadrant and the percentage of swimming distance in the platform quadrant were recorded.The animals were sacrificed after Morris water maze test.The density of normal neurons in ventral posterior inferior thalamic nucleus and hippocampal CA3 region in left and right cerebral hemisphere was measured and the ratio of the density of normal neurons in the left to right cerebral hemisphere was calculated.Results Compared with group Ⅰ,the escape latency was significantly prolonged at 30-34 days after HIBI in group Ⅲ and at 31 and 34 days after HIBI in Ⅳ group,the number of times the animals crossing the platform quadrant,percentage of time spent in the platform quadrant,percentage of swimming distance in the platform quadrant,and ratio of the density of normal neurons in the left to right cerebral hemisphere were decreased at day 35 after HIBI in group Ⅲ,no significant changes were found in the number of times the animals crossing the platform quadrant,percentage of time spent in the platform quadrant,and percentage of swimming distance in the platform quadrant,and the ratio of the density of normal neurons in the left to right cerebral hemisphere was decreased at day 35 after HIBI in group Ⅳ,and no significant changes were found in the parameters mentioned above in group Ⅱ.Compared with group Ⅲ,the escape latency was significantly shortened at 31-34 days after HIBI,and the number of times the animals crossing the platform quadrant,percentage of time spent in the platform quadrant,percentage of swimming distance in the platform quadrant,and ratio of the density of normal neurons in the left to right cerebral hemisphere were increased at day 35 after HIBI in group Ⅳ.There was no significant difference in the swimming speed and swimming distance at day 35 after HIBI between groups.Conclusion Isoflurane postconditioning can improve long-term cognitive function of neonatal rats with HIBI.