Role of hippocampal AMPK signaling pathway in reduction of postoperative cognitive dysfunction by stellate ganglion block in aged rats

Objective To evaluate the role of hippocampal AMP-activated protein kinase(AMPK)signaling pathway in reduction of postoperative cognitive dysfunction(POCD)by stellate ganglion block(SGB)in aged rats. Methods One hundred and twenty male Sprague-Dawley rats, aged 18-22 months, weighing 450-550 g, were randomly divided into 5 groups(n=24 each)using a random number table: sham operation group(group S); group POCD; group SGB; SGB + AMPK inhibitor group(group SI); AMPK inhibitor group(group AI). SGB was performed with 0.25% bupivacaine 0.15 ml in POCD, SGB and SI groups.Operation was performed at 15 min after the end of administration.Compound C(AMPK inhibitor)20 mg/kg was injected intraperitoneally at the end of surgery in groups SI and AI.Morris water maze test was performed at 1 day before operation and on 1, 3 and 5 days after operation.The escape latency and swimming distance were recorded.The rats were then sacrificed, and the brains were removed for determination of the expression of AMPK and phosphorylated AMPK(p-AMPK)by Western blot. Results Compared with group S, the escape latency and swimming distance were significantly prolonged, and the expression of AMPK and p-AMPK was down-regulated in POCD, SI and AI groups.Compared with group POCD, the escape latency and swimming distance were significantly shortened, and the expression of AMPK and p-AMPK was up-regulated in group SGB.Compared with group SGB, the escape latency and swimming distance were significantly prolonged, and the expression of AMPK and p-AMPK was down-regulated in SI and AI groups. Conclusion Activation of hippocampal AMPK signaling pathway is involved in SGB-induced reduction of POCD in aged rats. Key words: Protein-serine-threonine kinases; Stellate ganglion; Nerve block; Aged; Cognition disorders; Postoperative complications