Preliminary Study On The Effects Of Acupuncture At Different Tissues Beneath The Acupoints And The Possible Mechanisms

BACKGROUNDDeqi or needling sensations are the important signs of deqi responses induced by needling manipulations in clinical practice of acupuncture.Traditionally,deqi sensations can be divided into two types.The first one includes various sensations such as soreness,numbness,fullness,heaviness,temperature change(warmth or coolness),tingling,aching and dull pain felt by the participants;the second one is a"needle-grasping" sensation,the tightness,felt by acupuncturist,which is classically described as "like a fish biting on a fishing line".In clinic,the needling sensations felt by participant and the needle-grasping sensation felt by acupuncturist can be induced simultaneously sometimes,while under some circumstances the participant's needling sensations and acupuncturist's needle-grasping sensation occur separately.The fact above indicates that the mechanisms underlying the two types of deqi responses are somewhat different from each other.There have been many studies with attempt to illuminate the potential physiological basis of deqi sensations.As we know,the structures are the determinants of the functions.The previous studies have indicated that acupoint is a stereoscopic structure composed of various tissues including skin,muscle,connective tissue,nerve,blood vessel and so on.No special structures were found beneath the acupoint so far.Many studies have demonstrated that deqi sensations induced by acupuncture are associated with the different tissue structures beneath the acupoint.While the results of these studies were preliminary and even controversial.Actually,the potential physiological basis of deqi sensations is still unclear up to now.What's more,most of the previous studies have only focused on the deqi sensations felt by the patients or participants.There were fewer researches with emphasis on the mechanisms underlying the acupuncturist's needle-grasping sensation and so far there is almost no any studies aimed at the relationship between the deqi sensations felt by participants and that felt by acupuncturists.In resent years,functional magnetic resonance imaging(fMRI)was widely used on the brain mechanisms of acupuncture because of its no damaging,no radiation and high space resolution.However,the brain mechanisms underlying the different deqi sensations mediated by different tissue structures beneath the acupoints stimulated is not understood yet.The brain responses linking to the different kinds of deqi sensations,especially the central mechanisms underlying the involvement of muscles beneath the acupoints in the mediation of the deqi sensations needs to be further investigated.OBJECTIVEThe present study included three parts.The first one was to address the following points:1.What are the main needling/deqi sensations induced by acupuncture at different tissue structures(muscle,skin,etc.)beneath the acupoints stimulated.2 How about the brain responses and myoelectricity around the acupont stimulated during acupuncture stimulation at diffemet tissues beneath the acupoints stimulated The second part was designed to further explore the role played by the different tissue structures beneath the acupoint stimulated in the mediation of the needling sensations,especially to observe when the participants'and acupuncturist's needling sensations will occur simultaneously or separately,and what's the correlation between different needling sensations and the myoelectricity.Based on the above results,the third part of the present study was conducted in the rats to explore the possible role played by muscle spindle in the mediation of needling sensation felt by acupuncturist.METHODS1 Preliminary study on the needling sensations,myoelectricity around acupoints and brain responses induced by acupuncture stimulation at differnet tissuesbeneath the acupointsThirty-six healthy participants including male and female were recruited and all the participants were treated respectively with 4 kinds of the needling stimulations at Zusanli(ST36)and Dubi(ST35)once a week in 4 consecutive weeks,including superficial needling only at skin of ST36(the skin needling at ST36),deep needling penetrated to muscle layer at ST36 with local anesthesia of the skin around the acupoint by lidocaine cream(mainly muscle needling at ST36),deep needling penetrated to muscle layer at ST36 without local anesthesia of the skin around the acupoint(mainly skin and muscle needling at ST36)and needling at ST35 without local anesthesia of the skin around the acupoint.In the performance of the skin needling at ST36,the needle was inserted into the skin about 5mm at ST36,with the angle between the needle and skin about 15°.For the muscle needling at ST36,the needle was inserted vertically to a depth of 3 cm.For the skin and muscle needling at ST36,the needle was inserted vertically to a depth of 3 cm.Needling at ST35:the needle was inserted vertically to a depth of 1 cm.After insertion the needle was rotated clockwise and anticlockwise approximately 180° at 2 Hz for 30 seconds.Three times of 30-sencond needling rotation was performed in each participant and a 2-min interval was arranged between the two adjacent times of needling rotations.The acupuncturist's and participants' needling sensations during needling were collected and measured using the MGH Acupuncture Sensation Scale(MASS).The intensity and the occurrence rate of the soreness,pressure,heaviness,fullness,tingling,numbness,sharp pain,dull pain,warmth,coolness,and throbbing sensations in the participants'and tightness felt by the acupuncturist were measured individually and analyzed by SPSS 23.0.Surface electromyogram(sEMG)were recorded before the needle insertion,during needling manipulations and after needle withdrawal.The values of integrated EMG(IEMG)were calculated by LabChart 8.0 and analyzed by SPSS 23.0.The brain responses were measured by fMRI during needling and the activation or deactivation of the brain areas were analyzed by SPM8.2 The further study on the correlation between the acupuncturist's and participants' needling sensations and the possible role played by muscle.Similar to the aforementioned first part of the study,twenty healthy paticipants including male and female were recruited and all the participants were treated respectively with 4 kinds of the needling stimulations at Zusanli(ST36)and Dubi(ST35)once a week in 4 consecutive weeks.In this part of the study acupuncture manipulation was almost the same as that in the first part of the study except that in this part of study every participant was treated with only one time of 2-min needling manipulation.The acupuncturist's and participants' needling sensations were recorded by a sound recorder.The correlation between the participants' needling sensations and acupuncturist's tight feelings was analyzed.The electromyogram was recorded during needling and the IEMG values corresponding to the different needling sensations were analyzed.3 The effects of needling at different regions of muscle on acupuncturist's needling sensations and the possible mediating role played by muscle spindles.Ten male Sprague-Dawley rats were used in this part of study.The needling stimulation was given at different regions of the muscle(right tibialis anterior)and tendon around the ST36' namely the muscle belly,the distal tendon and the junctional area between the muscle and the tendon.The right tibialis anterior muscle was surgically exposed.The needle was rotated clockwise and anticlockwise approximately 1800 at 2 Hz for 1 minutes followed by a 1-min needle retention.Before,during and after needling the afferent discharge of the muscle spindle,myoelectricity and muscle tension of the tibialis anterior muscle were recorded and analyzed.The intensity of acupuncturist's tight sensation during needling was also measured.RESULTS1 Different needling sensations induced by acupuncture stimulation at different tissue structures beneath the acupoints1.1 Occurrence rate of needling sensations induced by acupuncture stimulation at different tissue structures beneath the acupointsDuring skin needling at ST36,the sharp pain,tingling and fullness occurred frequently in the participants.During muscle needling at ST36' the participants'fullness,dull pain,soreness and acupuncturist's tight feeling occurred frequently During skin&muscle needling at ST36,the participants'fullness,tingling,sharp pain,dull pain and acupuncturist's tight feeling occurred frequently.During needling at ST35,participants'fullness,tingling and sharp pain occurred frequently.The occurrence rate of acupuncturist's tight feeling during muscle needling at ST36 and skin&muscle needling at ST36 was significantly higher than that during skin needling at ST36 and needling at ST35(P<0.05).The occurrence rate of participants'dull pain during muscle needling at ST36 and skin&muscle needling at ST36 was significantly higher than that during skin needling at ST36(P<0.05).The occurrence rate of participants' dull pain during muscle needling at ST36 was significantly higher than that during needling at ST35(P<0.05).1.2 The effects of needling at different tissue structures beneath the acupoints on the intensity of needling sensationsDuring skin needling at ST36,the intensity of participants' sharp pain and tingling were strong.During muscle needling at ST36 and skin&muscle needling at ST36,the intensity of participants'fullness,dull pain,soreness and acupuncturist's tight feeling were strong.During needling at ST35,the intensity of participants' fullness,dull pain and sharp pain were strongThe intensity of participants' fullness,dull pain,soreness,MASS index and acupuncturist's tight feeling during muscle needling at ST36 and skin&muscle needling at ST36 were stronger than that during skin needling at ST36 and needling at ST35.Among these,the intensity of participants' fullness during muscle needling at ST36 and skin&muscle needling at ST36 were significantly stronger than that in group of skin needling at ST36(P<0.05);the intensity of acupuncturist's tight feeling of groups of muscle needling at ST36 and skin&muscle needling at ST36 was significantly stronger than that during skin needling at ST36 and needling at ST35(P<0.05);the intensity of participants' dull pain during muscle needling at ST36 was significantly stronger than that during skin needling at ST36(P<0.05).The intensity of participants'sharp pain during skin needling at ST36 was significantly stronger than that induced by muscle needling,skin and muscle needling and needling at ST35(P<0.05)2 The effects of the needling at different tissue structures beneath the acupoints on the IEMG valuesThe IEMG values during muscle needling and skin&muscle needling at ST36(P<0.05)were significantly higher than that before the needlings(P<0.05).No significant difference was found in the IEMG value during skin needling at ST36 and needling at ST35 as compared with that before the needlings(P>0.05).The IEMG values during muscle needling at ST36 and skin&muscle needling at ST36 were significantly higher than that during skin needling at ST36 and needling at ST35(P<0.05).3 The effects of needling at different tissue structures beneath the acupoints on brain responses detected by fMRISkin needling at ST36 elicited sparse activations and deactivations.The activated areas included bilateral middle frontal gyrus,thalamus;left inferior temporal gyrus,inferior parietal gyrus,angular gyrus;right inferior frontal gyrus(opercular)and supramarginal gyrus;the deactivations were identified in left precentral gyrus and postcentral gyrus.During the muscle needling at ST36 the activated and deactivated brain areas were obvious.The activated areas mainly located at bilateral inferior frontal gyrus(triangular and opercular),left superior temporal gyrus,right inferior parietal gyrus.The deactivated areas located at bilateral precentral gyrus,left postcentral gyrus,middle and inferior occipital gyrus,right superior parietal gyrus,parahippocampal gyrus and cuneus.During the skin and muscle needling at ST 36 the activated brain areas were extensive,including left middle frontal gyrus,inferior frontal gyrus(triangular),middle temporal gyrus,insula,thalamus,supplementary motor area and cerebellum,right inferior frontal gyrus(opercular),inferior parietal gyrus,cingulum gyrus.The deactivated brain areas included bilateral precentral gyrus and postcentral gyrus.Needling at ST35 activated different brain regions such as bilateral middle frontal gyrus,inferior frontal gyrus(opercular),supramarginal gyrus and right thalamus;and the needling also deactivated left precentral gyrus,postcentral gyrus and right postcentral gyrusAmong the aforementioned four kinds of needlings the difference in the brain responses of both activation and deactivation was found in bilateral middle frontal gyrus,thalamus;left inferior occipital gyrus;right calcarine,caudate and vermis4 The correlation between the participants' and acupuncturist's needling sensations4.1 The correlation of the intensity between the participants' and acupuncturist's needling sensations.There was a positive correlation of the intensity between the participants' fullness and acupuncturist's tight feeling during muscle needling at ST36(P<0.05,r=0.2572)and skin&muscle needling at ST36(P<0.05,r=0.4035).There was no correlation between acupuncturist's tight feeling and participants' other needling sensations respectively(P>0.05).There was also no correlation between acupuncturist's tight feeling and participants' needling sensations in other groups(P>0.05)4.2 The observation on the occurrence rate and time order of needling sensations felt by both participants and acupuncturist during needling at different tissues beneath the acupointsThe occurrence rates of acupuncturist's tight feeling during both the muscle needling at ST36 and the skin&muscle needling in ST36 were 100%.The needling-induced participants' needling sensations occurred prior to the acupuncturist's tight feeling at rates of 83.33%over the all records during both the muscle needling and the skin&muscle needling at ST36.A highest occurrence rate was found in the participants'fullness sensation which occurred prior to the acupuncturist's tight feeling at rates of 72.22%and 77.78%during both the muscle needling and the skin&muscle needling at ST36 respectively.The occurrence interval between the participants' fullness and acupuncturist's tight feeling was shortest.Based on the calculation the participants'fullness occurred only 5.62±1.39 s and 5.5±1.03 s earlier than the acupuncturist's tightness during both the muscle needling and during the skin&muscle needling at ST36 respectively.5 The correlation between the needling sensations and IEMG values.The IEMG values around the acupoint were 2-3 times of that before needling when the fullness,throbbing and dull pain or the tightness were felt by the participants or acupuncturist during both the muscle needling and the skin&muscle needling at ST36 respectively.There was no muscle activity during needling during the skin needling at ST36 and needling at ST356 The effects of the needling at different regions of the muscle on the activity of the muscle spindle,myoelectricity,muscle tension and acupuncturist's needling sensationsBefore needling at muscle belly,the discharge of muscle spindle was regular and stable,there was no obvious myoelectricity,and the muscle tension was also stable.During needling stimulation at muscle belly,the muscle spindle discharged regularly in a fast-slow alternant patern,which was accompanied with the obvious enhancement of both myoelectricity and muscle tension(P<0.05 as compared with those before the needling).There was no significant difference in the discharge of muscle spindle,IEMG values and muscle tension between during both needle retention and post-needling as compared with those before needling(P>0.05).During the needling at either tendon or the junctional region between muscle and tendon no significant difference in the discharge of muscle spindle,IEMG values and muscle tension during the periods of the needling stimulation,needle retention,post-needling as compared with those before needling(P>0.05).The occurrence rate and intensity of the acupuncturist's tight feeling were significant higher and stronger during needling at muscle belly than that during needling at either tendon or the junctional region between muscle and tendon(P<0.01).CONCLUSIONS1.Sharp pain and tingling are the main needling sensations when needling at skin of the acupoint.Fullness,dull pain,soreness and acupuncturist's tight feeling are the main needling sensations when needling mainly at muscle beneath the acupoint.2.The the needling-induced fullness in participants was always accompanied by acupuncturist's tight feeling when needling at the acupoint with rich muscles.Participants' fullness always occurred earlier than acupuncturist's tight feeling.Participants' fullness and acupuncturist's tight feeling are mainly related to muscle activities.3.Both the skin and muscle needling can induce brain activation and deactivation.The the skin needling and muscle needling could induce different brain responses mainly in the sensorimotor brain areas.The difference may be due partially to the different needling sensations induced by the needling at different tissues beneath the acupoint stimulated.4.More extensive deactivation detected by fMRI could be induced by the main deqi sensations produced by the muscle needling.Tingling and sharp pain may produce an opposite effect on deactivation.5.The needling at muscle belly may elicit acupuncturist's tight feeling more easily as compared with the needling at tendon and at the junctional region between muscle and tendon.It's likely that the acupuncturist's tight feeling may be due mainly to the myotatic reflex-mediated muscle contraction following the deformation of the muscle spinders induced by the needling stimulation.