Electroacupuncture "zusanli" - "yanglingquan Point Area The Treatment Of Chronic Pain, Cumulative Analysis Of The Effector Mechanisms

Objective: To observe the effect of electroacupuncture (EA) in the treatmentof chronic constrictive injury (CCI) pain and to explore its underlyingbiological mechanism of the accumulative effects, so as to provide experimentalevidence for clinical acupuncture therapy.Methods: Female Wistar rats were used in the present study.1) Electrophysiological experiments: Extracellular electrical activities ofneurons in hippocampal CA1 area were recorded in 30 anesthetized normal femalerats (25% urethane+ 1．5% chloralose) by using glass micropipettes for observingthe influences of EA at "Zusanli" (ST36) -"Yanglingquan" (GB34) on thespontaneous discharges of neurons.2) Behavior experiments: 91 rats were randomly divided into normal control group,ovariectomized (OVX)+CCI, OVX+CCI+EA 2days(2D), OVX+CCIEA 2weeks (2W) , CCI,CCI+ EA2D, CCI+EA2W groups, with 13 rats in every group. Memory damage modelwas made by ovary excision; learning memory abilities were tested by usingMorris water maze. CCI model was established by loose ligation of the sciaticnerve, the paw-withdrawal reaction upon radiant heat irradiation was measuredbefore every session of EA treatment (1mA, 2/15Hz) for 30 min.3) Expressions of choline-synthesizing enzyme choline acetyltransferase (ChAT)mRNA and Pro-opiomelanocortin (POMC) mRNA in the hippocampus CA1 area andventromedial hypothalamic region were determined by reversed reversetranscription polymerase chain reaction (RT-PCR) method for analyzing theeffect of EA on cellular transcription state of proteins related to theanalgesic efficacy and memory-ability in different groups.Results:1．There were three kinds of tendency about the changes of hippocampus neuron discharge after treating with 2Hz EA, excitement pattern (5/31, 16．13%) , inhibitory pattern (11/31, 35．48%) , unchanged pattern (15/31, 48．39%) . The results suggested that the influences of 2Hz EA on hippocampus neuron were mainly inhibitory, and the post-effect of EA still existed after cease of EA.2．There were three kinds of tendency about the changes of hippocampus neuron discharge after treating with 100Hz electro-acupuncture, excitement pattern(5/31, 16．13%) , inhibitory pattern (15/31, 48．39%) , unchanged pattern(16/31, 35．48%) . The results suggested that the influence of 100Hz EA onhippocampus neurons majorly was inhibitory, the post-effect of EA still existedafter 100Hz EA was ended, and no significant differences were found between100Hz and 2Hz EA in the therapeutic effect.3．Five weeks after ovary-excision, from the seventh day on, the escape latency of the rats in memory-undamaged group (5．57±3．26s) was significantly shorter than those in memory-damaged group (29．6810±8．34s) (P<0．01) . On the eighth day, the object quadrant terrace was taken off, the swimming time percent of staying in the object quadrant of OVX group (31．88±15．72%) was significantly less than that (44．16±12．99%)of group which the ovary of the rats wasn' t excised(P<0．05) ; the swimming distance percent in the object quadrant of OVX group (22．47±14．13%) was significant shorter than that in group (33．60±15．62%)which the ovary of the rats wasn't excised (P<0．05) .4．On the fourteenth day after CCI operation, results of paw-withdrawal latency suggested that the pain threshold (7．76±0．18s) in CCI model control group was significantly lower than that (11．65±0．37s) of normal control group(P<0．05) ; there were no significant differences between CCI+EA2D group (7．86±0．26s) and CCI model control group (7．76±0．18s) ; the paw-withdrawal latency(11．58±0．28s) of CCI+EA2W group was significantly longer than that (7．86±0．26s) of CCI+EA2D group (P<0．05) , the paw-withdrawal latency (7．43±0．49s) of 0VX+CCI model control group was significantly shorter than that(11．65±0．37s)of normal control group(P<0．05) ; and no remarkable differences were found between OVX+CCI EA2D group (7．47±0．33s) and OVX+CCI group (7．43±0．49s) ; latency (11．58±0．28s) of OVX+CCI+EA2W group (8．40±0．84s) wasevidently longer than that (8．40±0．84s) of OVX+CCI+EA2D group (7．47±0．33s)(P<0．05) and latency (11．58±0．28s) of CCI+EA2W group was evidently longerthan that (8．40±0．84s) of OVX+CCI+EA2W group (P<0．05) .5．Compared with normal control group, POMC mRNA expression in hypothalamus in CCI model control group (0．97±0．18) was significantly higher than that of normal control group(0．53±0．11) (P<0．05) ; and there were no obvious difference between the CCI EA2D group (1．00±0．20) and CCI model control group (0．97±0．18, P>0．05) ; POMC mRNA expression in CCI+EA2W group (1．45±0．31) was significantly higher than that of CCI+EA2D group (1．00±0．20) ( P<0．05) , no significant difference was found between the OVX+CCI model control group (0．74±0．13) and the normal control group (0．53±0．11) (P>0．05) ; there were no marked difference between OVX+CCI EA2D group(0．69±0．11) and the OVX+CCI model control group (0．74±0．13) (P>0．05) . POMC mRNA expression in ventromedial hypothalamic region in rats of OVX+CCI+EA2W group (0．94±0．08) was significantly higher than those of OVX+CCI+EA2D group (0．69±0．11) (P<0．05) ; and the CCI+EA2W group(1．45±0．31) was remarkably higher than that of OVX+CCI+EA2W group (0．94±0．08) (P<0．05) . It suggested that after CCI, POMC mRNA expression was upregulated significantly, and after EA, the expression of POMC mRNA was upregulated further; while following OVX, the effect of EA was weakened significantly.6．In comparison with normal control group (0．65±0．17) , ChAT mRNA expression in hippocampal in CCI model control group ( 0．88±0．18 ) increased significantly(P<0．05) ; and there were no significant difference between the CCI EA2D group (0．89±0．17) and CCI model control group (0．88±0．18) (P>0．05) . ChAT mRNA expression in CCI+EA2W group (1．47±0．34) was significantly higher than that (0．89±0．17) of CCI+EA2D group (P<0．05) . No apparent differences were found among OVX+CCI model group (0．70±0．18) and normal control group (0．65±0．17) and OVX+CCI EA2D group (0．75±0．17) (P>0．05) in ChAT mRNA expression. No apparent differences were found among OVX+CCI+EA2W group (0．96±0．10) and OVX+CCI+EA2D group (0．75±0．17) (P>0．05) in ChAT mRNA expression. Results displayed that following CCI, ChAT mRNA expression was upregulated considerably, and after EA for 2 weeks, the expression was strengthened further, while after OVX, the effect of EA was lowered.7．ChAT mRNA expression in hypothalamus in CCI model group (0．94±0．09) was no significant difference between CCI EA2D group(1．01±0．13) and normal control group (0．87±0．11) (P>0．05) . ChAT mRNA expression in CCI+EA2W group (1．46±0．23) was significantly higher than that (1．01±0．13) of CCI+EA2D group(P<0．05) . While compared with CCI model group (0．65±0．27) , ChAT mRNA expression in CCI+EA2W group (1．46±0．23) was potentiated further (P<0．05) ; and no significant difference was found between the OVX+CCI model group (0．65±0．27) and OVX+CCIEA2D group (0．64±0．15) (P>0．05) ; there were no differences between the OVX+CCI+EA2D group (0．64±0．15) and the OVX+CCI model group (0．65±0．27) (P>0．05) . The changes of ChAT mRNA expression in hypothalamus in different groups were similar to those of hippocampal.Conclusion:1．The information of 2Hz and 100Hz EA of "Zusanli"-"Yanglingquan" can be delivered to the hippocampus CA1 area, and significantly affect electrical activities of most neurons there.2．For CCI rats, EA at "Zusanli"-"Yanglingquan" , two days treatment couldn't significant improve pain threshold, but two weeks' treatment could significantly relieve pain, suggesting appearance of the accumulative effect following 2 weeks' EA; while after OVX, the analgesic effect of EA was weakened apparently.3．Following CCI, POMC mRNA expression and ChAT mRNA were upregulated significantly and after EA for 2 weeks (not 2 days) their expression increased further and significantly. Hence, longer EA treatment has a marked accumulative effect in relieving chronic pain, which is closely to its effects in upregulating the expression of PKC, VAChT, and ChAT mRNA in hippocampal CA1 and VMH regions, and POMC mRNA expression in VMH region and the neuronal memory ability.