Effects of inhalation of isoflurane at different time points on hypoxic-ischemic brain injury in neonatal rats

Objective To investigate the effects of inhalation of isoflurane at different time points on hypoxic-ischemic brain injury in neonatal rats.Methods One hundred and eighty 7-day-old Sprague-Dawley rats,weighing 12-16 g,were randomly divided into 6 groups (n =30 each):sham operation group (group Ⅰ),cerebral hypoxia/ischemia (H/I) group (group Ⅱ),and inhalation of isoflurane at different time point groups (groups Ⅲ-Ⅵ).Brain ischemia was induced by double ligation of left common carotid artery followed by inhalation of 8 ％ O2 + 92 ％ N2 for 2 h at 37 ℃.In groups Ⅲ,Ⅳ,Ⅴ and Ⅵ 1.5 ％ isoflurane was inhaled for 30 min starting from 0,3,6,12 h after H/I respectively,while the rats were exposed to 30％ O2 and 70％ N2 only in groups Ⅰ and Ⅱ.The survival rate at 7 days after H/I was recorded.The animals were sacrificed at 7 days after H/I.The brains were removed and the right and left cerebral hemispheres (CH) were weighed separately.The ratio between left/right CH was calculated.The density of normal neurons in ventral posterior inferior thalamic nucleus and posterior cingulate cortex in left and right CH were measured and the ratio of the density of normal neurons in the left to right CH was calculated.Results Compared with group Ⅰ,the weight of left cerebral hemisphere,ratio between left/right CH,and ratio of the density of normal neurons in the left to right CH were significantly decreased in other five groups (P ＜ 0.05).Compared with group Ⅱ,the weight of left cerebral hemisphere,ratio between left/right CH,and ratio of the density of normal neurons in the left to right CH were significantly increased in groups Ⅲ,Ⅳand Ⅴ (P ＜ 0.05).There were no significant differences in the indices nentioned above among groups Ⅲ,Ⅳand Ⅴ (P ＞ 0.05).There was no significant difference in the survival rate among groups Ⅱ-Ⅵ (P ＞ 0.05).Conclusion Inhalation of 1.5％ isoflurane for 30 min within 6 h after cerebral H/I can reduce the cerebral injury in neonatal rats. Key words: Isoflurane; Hypoxia-ischemia, brain; Infant, newborn