Effects of surgical trauma on synaptic structure in hippocampal CA3 area in aged rats / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effects of surgical trauma on synaptic structure in hippocampal CA3 area in aged rats.Methods Fifty-six healthy SD rats aged 18 months were randomly divided into 3 groups control group (group C, n = 8) , anesthesia group (group A, n = 24) , and operation group (group O, n - 24) . Anesthesia was performed with intraperitoneal ketamine 40 mg/kg but no operation was carried out in group A. Anesthesia was also performed with intraperitoneal ketamine 40 mg/kg, and splenectomy was performed after loss of righting reflex in group O. Eight animals from group A and O selected on 1, 3, and 7 d after anesthesia or operation respectively underwent Morris water maze test for assessment of the cognitive function. The animals were . then decapitated. Hippocampal CA3 area was isolated for examination with electron microscope and the synaptic structure in the polymorphic layer of hippocampal CA3 area was measured. Results Compared to group C and A, the times of passing through the original platform and number of synapses were significantly reduced, the width of synaptic cleft was significantly increased, the thickness of the postsynaptic density was significantly decreased, the length of the active zones was significantly shortened, and the curvature of the synaptic interface and percentage of perforated synapses were significantly decreased at T_(1,2), ( P < 0.05 or 0.01) , but no significant change was found in the indices mentioned above at T_3 in group O(P > 0.05). Compared to group C, the latency and swimming distance were significantly prolonged at T_1 in group A and at T_(1,2) in group O ( P < 0.01) . Compared to group A, the latency at T_(1,2) and the swimming distance at T_2 were significantly prolonged in group O ( P < 0.05) . Conclusion Surgical trauma can induce early postoperative cognitive impairment through changing synaptic structure in hippocampal CA3 area in aged rats.