Effects Of Electroacupuncture With Different Waveforms On Postoperative Cognitive Dysfunction After Partial Hepatectomy In Old Rats

Background and Objective:Postoperative cognitive dysfunction(POCD)is one of common complications in the Central Nervous System(CNS)after operation,especially in elderly patients with high incidence,which can lead to a long-term or permanent cognitive impairment,decline and even loss of life self-care ability.Notedly,the incidence of POCD is closely relative to the long-term mortality after operation and it burden to larger families and the society.Scholars have done a lot of studies on the mechanism of POCD,but the specific mechanism is still not fully elucidated,and it also has no the ideal method of prevention.Studies have suggested that surgical trauma can cause local cerebral inflammation or systemic inflammation.The latter is a kind of cascading inflammation and it can lead to the occurrence and development of POCD.Microglia is a kind of inherent and congenital immune cell in the CNS.For many years,it is thought to be involved in neurodegenerative disease and cerebral inflammation.When being activated by peripheral inflammation,microglia can produce cytotoxic factors including tumor necrosis factor(TNF)-? and Interleukin(IL)-6,nitric oxide and reactive oxygen species(ROS),resulting in neuronal cell apoptosis accompanied by neurodegeneration.The cytotoxic factor released from microglia is also involved in a variety of pathophysiological process,such as organ ischemia-reperfusion injury and inflammation,but its participation in the occurrence of POCD caused by partial hepatectomy has yet to be report.Acupuncture is an important method in traditional medicine,characterized by easy operation,clear efficacy,economic security,and no side effects,which attracts wide attentions in medical field.Furthermore,according to the patient's concrete condition,individualized treatment can be conducted by choosing acupoint properly for increasing efficacy.On the basis of the traditional acupuncture,electroacupuncture(EA)takes effect by changing parameters of electrical stimulation.It has been proved that EA has preventive and therapeutic effects on heart,kidney,and brain injuries.It could improve learning and memory function by regulating the immune system,anti-inflammation,antioxidant,anti-apoptosis,and so on.Our previous study has also confirmed that the EA of limb ischemia reperfusion brain injury had a protective effect by reducing the microglia activation and inhibiting oxidative damage and inflammatory reaction.The parameter is an important factor influencing and changing EA response and its mechanism,including waveform,frequency,and strength of output impulse.The EA parameter has great influence on efficacy,leading to different responses in body function.Therefore,different parameters should be chosen for different diseases to achieve the best efficacy.In previous studies on the effect of EA in the central nervous system,the waveform used was mainly dilatational wave,very few studies used continuous or discontinuity waves.However,studies on the treatment of POCD using EA are limited,and the effects of different waveforms on POCD and its mechanism are still unclearIn the present study,an old rat model of POCD was built by partial hepatectomy to observethe the role of the microglia in POCD caused by partial hepatectomy and the efficacy difference in the POCD treated by electroacupuncture with different waveforms,and explore the relevant mechanism.It is helpful to clinical for developing new drugs on microglial activation to prevent POCD.On the other hand,it can provide theoretical basis for the protection of EA with different waveforms.Methods: One hundred and twenty healthy old Wistar rats were randomized into 5 groups(n=24): sham group,operation group and EA groups(continuous wave,disperse-dense wave and discontinuity wave).Partial hepatectomy model were produced,preoperative electrical stimulations with different waveforms were applied to Baihui and Dazhui points for 30 min/once,once daily,continuously for 3 days.The cognitive function was tested using Morris water maze(MWM)method at day 1,day 2 and day 5 after operation.Brain tissue was harvested at day 2 for detection of microglia by immunohistochemistry.The protein level of Iba-1(a marker of microglia)in hippocampus was measured by Western blot.The concentrations of ROS,MDA,IL-?,IL-6 and TNF-?,and the SOD activity in hippocampus were measured.The apoptosis was detected by TUNEL method,then the apoptosis index was calculated.Results:(1)Cognitive function: Compare with S group,the escape latency and the swimming distances increased,the times of crossing the previous platform reduced decreased in O,CW,DW and IW groups(p<0.05).Compare with O group,the escape latency and the swimming distances decreased,and the crossing the previous platform times increased in all EA groups(p<0.05).CW,DW and IW groups had statistical difference each other(DW>IW>CW)(p<0.05).(2)The microglia in hippocampus: Compare with S group,the number of Iba-1 positive cells,the percent of activated microglia and Iba-1 protein expression in O,CW,DW and IW groups increased significantly(p<0.05).Compare with O group,the number of Iba-1 positive cells,the percent of activated microglia and Iba-1 protein expression in three EA groups reduced(p<0.05).(DW>IW>CW,p<0.05).(3)The IL-1??IL-6 and TNF-? levels in hippocampus: Compare with S group,the IL-1??IL-6 and TNF-? levels in O group and three EA groups(CW,DW and IW)increased significantly(p<0.05).However,compare with O group,the levels of IL-1??IL-6 and TNF-? decreased in CW,DW and IW groups(p<0.05).The results showed: DW>IW>CW.(4)The hippocampal ROS,MDA levels and SOD activity: Compare with S group,the levels of ROS,MDA elevated and SOD activity lowered in O group and three EA groups(CW,DW and IW)significantly(p<0.05).Compare with O group,these indexes had improved in CW,DW and IW groups(p<0.05).For improvements,the sequence from high to low is:DW,IW,CW(p<0.05).(5)cell apoptosis: Few apoptotic cells could be detected in S group(low apoptosis index).However,a lot of apoptotic cells could be observed in O group(high apoptosis index).Compare with S group,the apoptosis index in O,CW,DW and IW groups were higher(p<0.05).Compared with O group,the apoptosis index in all EA groups were lower(p<0.05).For improvements,the sequence from high to low is:DW,IW,CW(p < 0.05).Conclusion:(1)Partial hepatectomy can lead to cognitive dysfunction,induce microglia activation and prompte inflammatory factors,oxidative stress injury and cell apoptosis increases in hippocampus in old rats.(2)EA pretreatment at ‘Baihui' and ‘Dazhui' acupoints with different waveforms can prevent POCD,and the effect of dense-disperse wave more than that of intermittent wave,the latter is superior to continuous wave.(3)The mechanism of EA on cognitive improvement against POCD may be related with inhibiting microglial activation,attenuating inflammation,oxidative stress and cell apoptosis in hippocampus.