Effect of isoflurane on synaptophysin expression in hippocampal CA3 area in aged rats

Objective To investigate the effect of isoflurane on the synaptophysin expression in hippocampal CA3 area in aged rats. Methods Sixty-three 24-month-old SD rots, weighing 400-650 g, were randomly divided into 3 groups (n=21 each): control group (group C), 1.2% isoflurane group (group E_1), and 1.8% isoflurane group (group E_2). The rats in group C only inhaled a gas mixture containing 40% oxygen for 3 h. The rats in group E_1 and E_2 inhaled 3% isoflurane for induction, and after righting reflex disappeared, the concentration was reduced to 1.2% and 1.8% respectively which was maintained for 3 h. Twelve rats randomly selected from each group underwent Morris water maze teat for assessment of learning and memory function (escape latency and probe time). The training test was performed 4 times a day for 7 d. Nine rats randomly selected from each group were decapitated at day 1,3, and 7 after the termination of anesthesia. The hippocampal CA3 area was isolated for determination of synaptophysin expression. Results The escape latency was significantly longer at day 2 and 3 after the termination of anesthesia in group E_1 and E_2 than in group C (P 0.05). The synaptophysin expression in hippocampal CA3 area was significantly lower in group E_1 and E_2 than in group C (P 0.05). There was no significant difference in escape latency between group E_2 and group E_1 (P > 0.05), and the synaptophysin expression in hippocampal CA3 area was significantly lower in group E_2 than in group E_1 (P < 0.01). Conclusion The cognitive dysfunction induced by isoflurane anesthesia in aged rats is not related to the synaptophysin expression in hippocampal CA3 area. Key words: Isoflurane;  Synaptophysin;  Cognition disorders;  Aged