Relationship between mechanism underlying electro-acupuncture-induced improvement of postoperative cognitive dysfunction and mitochondrion-dependent apoptosis in hippocampal neurons of aged rats

Objective To evaluate the the relationship between the mechanism underlying electro-acupuncture(EA)-induced improvement of postoperative cognitive dysfunction and mitochondrion-dependent apoptosis in hippocampal neurons of aged rats. Methods Seventy-two healthy male Sprague-Dawley rats, aged 18 months, weighing 500-550 g, were divided into 3 groups(n=24 each)using a random number table method: control group(group C), operation group(group O)and group EA.EA was performed at Baihui and Dazhui acupoints for 30 min using disperse-dense waves, with a frequency 2/15 Hz and intensity 1 mA, once a day for 5 consecutive days in group EA.Laparotomy was performed under 3% sevoflurane anesthesia after the end of EA stimulation in O and EA groups.Morris water maze test was performed on 1 day before operation and 3 and 7 days after operation to assess the cognitive function.Rats were sacrificed after the end of Morris water maze test, brains were removed, and hippocampal tissues were obtained for detection of apoptosis rate of hippocampal neurons and expression of hippocampal caspase-3 and cytochrome c(Cyt c)by Western blot. Results Compared with group C, the escape latency was significantly prolonged after operation, the frequency of crossing the original platform was reduced, the apoptotic rate of hippocampal neurons was increased, and the expression of caspase-3 and Cyt c was up-regulated in O and A groups(P<0.05). Compared with group O, the escape latency was significantly shortened after operation, the frequency of crossing the original platform was increased, the apoptotic rate of hippocampal neurons was decreased, and the expression of caspase-3 and Cyt c was down-regulated in EA group(P<0.05). Conclusion The mechanism by which EA improves postoperative cognitive dysfunction may be related to inhibiting mitochondrion-dependent apoptosis in hippocampal neurons of aged rats. Key words: Electro-acupuncture; Cognition disorder; Neurons; Mitochondria; Apoptosis