Effect of stellate ganglion block on postoperative synaptic structure in hippocampal CA3 region in aged rats

Objective To evaluate the effect of stellate ganglion block (SGB) on postoperative synaptic structure in hippocampal CA3 region in aged rats.Methods Seventy-two male Sprague-Dawley rats,aged 20-22 months,weighing 550-650 g,were randomly divided into 3 groups (n =24 each) using a random number table:control group (group C),operation group (group O) and SGB + operation group (group SGB).Group SGB received right SGB with 0.25％ bupivacaine 0.15 ml.Groups O and SGB underwent 30 min of exploratory laparotomy starting from 15 min after the end of administration.Y-maze test was performed on 1 day after operation in 6 rats chosen from each group for assessment of cognitive function.The frequency of standard training and standard time were recorded.Six rats were chosen from each group on 1,3 and 7 days after operation and sacrificed and the hippocampal CA3 region was isolated for microscopic examination and for measurement of synaptic structure.Results Compared with group C,the standard time was significantly prolonged,and the frequency of standard training was increased in groups O and SGB,the width of synaptic cleft was increased,the thickness of post-synaptic density was decreased,the length of active zones was shortened,and the curvature of the synaptic interface was decreased on 1,3 and 7 days after operation in group O (P ＜ 0.05),and no significant changes were found in each synaptic structure parameter in group SGB (P ＞ 0.05).Compared with group O,the standard time was significantly shortened,the frequency of standard training was decreased,the width of synaptic cleft was decreased,the thickness of the post-synaptic density was increased,the length of active zones was prolonged,and the curvature of the synaptic interface was increased on 1,3 and 7 days after operation in group SGB (P ＜ 0.05).Conclusion The mechanism by which SGB improves the postoperative cognitive dysfunction in aged rats may be related to inhibition of changes of synaptic structure in hippocampal CA3 region. Key words: Stellate ganglion;  Nerve block;  Aged;  Hippocampus;  Synapses