The Relationship Between Acupoints Sensitization And Sympathetic-sensory Coupling Caused By Myocardial Ischemia

BackgroundIt has been well established in traditional Chinese medicine that acupoint,which has diagnostic and curative effect on diseases,is an important position for the correlation between meridian and visceral organs.Recently,previous studies have reported that many sensitized points in somatic can be observed in visceral diseases,which are very close to acupoint regions.Some scholars suppose that acupoint is sensitized area in the body and performs neurogenic inflammation under pathological conditions,which is also named acupoint sensitization.Stimulating these sensitized acupoints could improve the related visceral functions via neuro-endocrine pathway,and then promote the regulation of homeostasis.Sympathetic nervous system?SNS?plays a vital role in the maintenance of homeostasis,because almost vital organ's functions are charged by SNS.It is reported recently that SNS activity was affected in conditions,e.g.myocardial ischemia caused cardiac SNS hyperactivity and sympathetic nerve sprouting.However,the correlation among the process of self-healing in visceral disease,the activity of SNS and sensitized acupoint remains unclear.What's more,it has been confirmed that acupuncture plays a positive role in the treatment of visceral dysfunctions.Therefore,the present research aims to further explore the relation among the three mentioned parts and the possible role of acupuncture,it is important to study the nature of acupoint and the mechanism of acupuncture stimulation.ObjectiveThe present study aims to investigate the correlation among visceral diseases,SNA?sympathetic nerve activity?and acupoint sensitization,and the role of acupuncture in the regulation of the mentioned relationship.In this study,myocardial ischemia rats were selected as experimental model,observed:1)the change of somatic sensitized point and SNA after MI modeling;2)the change of SNA influenced by the afferent of somatic sensitized points,and the effect of stimulating sensitized point on SNA under pathological conditions;3)the phenomenon of sympathetic nerve sprouting and sympathetic-sensory coupling in chronic MI model rats;4)the correlation between the positive role of EA application on MI model and SNA.MethodsMI models was established by ligating levo-anterior descending branch of coronary artery in SD rats.The present study consisted of five sections:The aim of the first section is to study the influence of cardiac diseases on somatic sensitized points and its'distributing characteristics.Eighteen healthy male SD rats were randomly divided into Control?n=6?and AMI?n=12?group.Rats in AMI were treated with AMI modeling.Then rats in both groups were injected Evans blue?EB?into caudal vein,observed the EB leakage point in skin via Fluorescence-labeled Organism Bioimaging technology,and measuring the change of pain thresholds via Von Frey.The aim of the second section is to verify the influence of MI-operation,the afferent of sensitized point sensory and noxious stimulus on cardiac SNA under pathological condition via nerve electrophysiological and HRV recording.The third section is intended to study the phenomenon of sympathetic nerve sprouting and sympathetic-sensory coupling in left DRG and skin at same spinal segment in chronic MI model,using immunofluorescence?IF?and Western Blotting?WB?tests.Thirty-two healthy male SD rats were randomly divided into Control,MI 3 d,MI 7 d and 28 d group?n=8?.Observing the change of TH and CGRP positive neurons or nerves in adjacent segmental DRG and skin,and meanwhile investigating the correlation between the sympathetic nerve sprouting and the course of MI disease.The aim of the fifth section is mainly to verify the relation between the effect of EA on chronic MI disease and SNA activity.Eighty healthy male SD rats were randomly divided into model,EA,Atenolol and Atropine group.EA treatment?15Hz,1.5 mA,20 min?at bilateral PC 6 was applied once a day in28 consecutive days to EA group.The rats in Atenolol and Atropine group were received the injection of atenolol?4 mg/Kg,i.p.,2 times/d?and atropine?4mg/Kg,i.p.,2 times/d?for 28 consecutive days,respectively.Through recording ECG and using Doppler echocardiography?TTDE?,observing the change of ST height in ECG,EF and FS level were measured at baseline,post-operation,7 d,14 d?21 d and 28 d after operation.Finally,cardiac SNA,dp/dt_maxax and dp/dt_minin were elevated by neuro electrophysiological technology and Millar catheter.Results1.The influence of MI-operation on EB leakage point and its'distribution.The distribution of EB leakage points after MI-operation mainly appeared at the same and adjacent segmental spinal innervation area to heart.In contrast,no EB leakage points were observed in Control group.The pain threshold of EB leakage was obviously lower than contralateral non-leakage point?P<0.001?.Therefore,the results indicated that acute MI can cause sensitized points at same and adjacent spinal innervation area to the organ.2.The influence of MI operation,the afferent of somatic sensitized points and noxious stimulus on SNA in acute MI model rats.After MI surgery,SNA and LF/HF ratio were both obviously accelerated compared to baseline?P<0.001?;Compared to the level of MI-operation,noxious stimulus?pinch,EA and thermal?applied at somatic sensitized could increase the activity of cardiac SNA,and positively regulate the level of LF/HF ratio?P<0.05?.However,cardiac SNA and LF/HF ratio were attenuated after clipping left brachial plexus compared with post-MI operation.Therefore,the results indicated that visceral dysfunction could cause SNS hyperactivity which was related to the afferent of somatic sensitized points.Meanwhile,although somatic noxious physical stimulus at sensitized points could further increase SNA under pathological condition,it played a positive role in sympathetic and parasympathetic nerve balance.3.The change of sympathetic activity and sympathetic-sensory coupling in chronic MI model ratsCompared with post-MI operation,cardiac SNA and LF/HF ratio were eventually decreased in chronic MI model rats?P<0.05?.The IF tests showed that a lot of TH positive nerve fibers?sympathetic nerve?sprouting in DRG and skin at the same segments in MI 3 d,7 d and 28 d groups compared to control group.Moreover,TH positive nerves were surrounding sensory neurons in DRG and then forming sympathetic-sensory coupling in chronic MI rats.Furthermore,results of WB tests showed that the level of TH in DRG and skin,CGRP in skin were significantly increased after MI operation.Therefore,the present results proposed that the process of self-healing was activated by SNS hyperactivity during visceral dysfunction.Meanwhile,SNA also was contributed to the regulation of visceral hemostasis via sympathetic never sprouting.4.The mechanism of EA application at PC 6 on the recovery of ST height and cardiac function in chronic MI rats.4.1 The comparison of survival rate among groupsThe death of MI rats mainly happened at 7 d after modeling.Although the survival rate of EA and Atenolol groups were higher than the others,there was no statistical difference?P>0.05?.In details,the survival rate of Model group was 50%,55%for EA group,70%for Atenolol group,and 45%for Atropine group.4.2 The influence of EA application at PC 6 on cardiac SNA of chronic MI ratsCompared with Model group,cardiac SNA of MI rats in EA and Atenolol group were obviously decreased?P<0.05?,while Atropine group showed a higher SNA than that in Model group?P<0.05?.The results showed that EA on PC 6 could improve the status of SNS hyperactivity during cardiac diseases via regulating?₁ receptor.4.3 The influence of EA application at PC 6 on ST height of chronic MI ratsRepeated measures two-way ANOVA showed that compared with Model and Atropine group respectively,EA intervention at PC 6 promoted the recovery of ST height,there were significantly difference in group,time and group*time effect between groups?P<0.05?.However,no statistical difference was observed in comparison between EA and Atenolol group.It indicated that EA intervention at PC 6 could promote the process of self-healing in MI model via affecting the expression of?₁ receptor.4.4 The influence of EA application at PC 6 on EF and ES in chronic MI ratsRepeated measures two-way ANOVA showed that only significant difference in group effect was observed in EA compared with Model,Atenolol and Atropine group respectively?P<0.05?.These results indicated that although EA could improve cardiac function via regulating the expression of?₁ receptor,there were other factors involving in the mechanism.4.5 The influence of EA application at PC 6 on dp/dt_max?dp/dt_min in chronic MI ratsCompared with Model group,the level of dp/dt_max and dp/dt_min in EA and Atenolol group were significantly improved?P<0.05?,which indicate that EA application could enhance cardiac function via regulating the expression of?₁receptor.However,no statistical difference was observed between Model and Atropine group?P>0.05?.It indicated that the self-healing function was related to cardiomyocyte M receptor activity during cardiac disease.Conclusion1.The phenomenon of sensitized points at same or adjacent somatic segment were caused by myocardial ischemia,the afferents of which are related to SNS hyperactivity in pathological state.2.SNS hyperactivity caused by MI activates the mechanism of self-healing,and meanwhile MI modeling caused sympathetic sprouting and sympathetic-sensory coupling in DRG and skin at adjacent spinal segmental,which plays a role in self-healing process.3.Stimulation of homotopic sensitized points mainly performs a role of augmenting SNA,however,which plays a promoting role in the regulation of hemostasis between sympathetic and parasympathetic nerve system.4.The low survival rate is related to sympathetic nervous hyperactivity during chronic MI,while parasympathetic nervous system plays a positive role in the self-healing process of cardiac dysfunction.5.Through regulating the cardiomyocyte?₁ and M receptor,EA application at PC 6 decreases the status of cardiac SNS hyperactivity,improves the self-healing ablitity and promotes cardiac function recovery.