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ObjectiveThe objective of this study is to observe the effects of mild mechanical stimulation on acupuncture points of spinal motor neurons and active substances of sciatic nerve injury in rats, and to explore the morphological basis for the recovery of motor function in rats with sciatic nerve injury, using mild acupuncture. Acupuncture in the local area of injury may cause further damage to the peripheral nerve injury. We believe that mild mechanical stimulation on the surface, using some specific acupuncture points can also have a positive effect on nerve repair. This method, called Chinese tuina, has existed for more than 2,000 years in China.MethodsThis study establishes a rat model using sciatic nerve crush injury. Rats received Chinese tuina in accordance with the principle of the three methods and three points, once a day, for 20 days. The rats’ status of hindlimb recovery was detected by a sciatic functional index. The labeled neuronal cell body was used to evaluate the fiber recovery after the rats’ sciatic nerve injury, using a neural tracing technique. Our team studied motor neuronal cell bodies, CGRP-positive cells, and the microglia of damaged sciatic nerves which were stained with fluorescent triple staining, adopting a confocal multi-layer scanning technique, and then the changes in neuronal activity distribution and expression, and changes of time and treatment were described, using the method of morphological description.ResultsSciatic nerve injury decreased the survival rate of motor neurons, affected CGRP-positive cells, and activated microglia in the ventral horn of the spinal cord. Compared with the model group, the survival of spinal ventral horn motor neurons was increased through tuina intervention. The swelling of CGRP-positive cells was alleviated, and the degree of microglia activation was less than that of the model group.ConclusionThis study used visual morphological findings to assess changes in neurons and active substances with time after injury of the peripheral nerve, and demonstrated that peripheral mild acupuncture intervention improved the capacity of neurofibrillary axoplasmic transport, regulated microglia activation, and significantly promoted the recovery of sciatic nerve injury.

Conditional gene editing animals and viral vectors have been widely applied in the research fields of biology and medicine. Recently, they are also used as the effective approaches to reveal the underlying mechanism of acupuncture from the nervous system to the specific molecules. In order to further understand the application of conditional gene editing animals and viral vectors, in this article, we analyze their characteristics, advantages and recent development in the field of acupuncture research and discuss their potential roles and prospect in the future.

Pericytes, as the mural cells surrounding the microvasculature, play a critical role in the regulation of microcirculation; however, how these cells respond to ischemic stroke remains unclear. To determine the temporal alterations in pericytes after ischemia/reperfusion, we used the 1-hour middle cerebral artery occlusion model, which was examined at 2, 12, and 24 hours after reperfusion. Our results showed that in the reperfused regions, the cerebral blood flow decreased and the infarct volume increased with time. Furthermore, the pericytes in the infarct regions contracted and acted on the vascular endothelial cells within 24 hours after reperfusion. These effects may result in incomplete microcirculation reperfusion and a gradual worsening trend with time in the acute phase. These findings provide strong evidence for explaining the "no-reflow" phenomenon that occurs after recanalization in clinical practice., Competing Interests: None

Neural tract tracing is used to study neural pathways and evaluate neuronal regeneration following nerve injuries. However, it is not always clear which tracer should be used to yield optimal results. In this study, we examined the use of Alexa Fluor 488-conjugated cholera toxin subunit B (AF488-CTB). This was injected into the gastrocnemius muscle of rats, and it was found that motor, sensory, and sympathetic neurons were labeled in the spinal ventral horn, dorsal root ganglia, and sympathetic chain, respectively. Similar results were obtained when we injected AF594-CTB into the tibialis anterior muscle. The morphology and number of neurons were evaluated at different time points following the AF488-CTB injection. It was found that labeled motor and sensory neurons could be observed 12 hours post-injection. The intensity was found to increase over time, and the morphology appeared clear and complete 3-7 days post-injection, with clearly distinguishable motor neuron axons and dendrites. However, 14 days after the injection, the quality of the images decreased and the neurons appeared blurred and incomplete. Nissl and immunohistochemical staining showed that the AF488-CTB-labeled neurons retained normal neurochemical and morphological features, and the surrounding microglia were also found to be unaltered. Overall, these results imply that the cholera toxin subunit B, whether unconjugated or conjugated with Alexa Fluor, is effective for retrograde tracing in muscular tissues and that it would also be suitable for evaluating the regeneration or degeneration of injured nerves., Competing Interests: None

The mouse model of multiple cerebral infarctions, established by injecting fluorescent microspheres into the common carotid artery, is a recent development in animal models of cerebral ischemia. To investigate its effectiveness, mouse models of cerebral infarction were created by injecting fluorescent microspheres, 45-53 µm in diameter, into the common carotid artery. Six hours after modeling, fluorescent microspheres were observed directly through a fluorescence stereomicroscope, both on the brain surface and in brain sections. Changes in blood vessels, neurons and glial cells associated with microinfarcts were examined using fluorescence histochemistry and immunohistochemistry. The microspheres were distributed mainly in the cerebral cortex, striatum and hippocampus ipsilateral to the side of injection. Microinfarcts were found in the brain regions where the fluorescent microspheres were present. Here the lodged microspheres induced vascular and neuronal injury and the activation of astroglia and microglia. These histopathological changes indicate that this animal model of multiple cerebral infarctions effectively simulates the changes of various cell types observed in multifocal microinfarcts. This model is an effective, additional tool to study the pathogenesis of ischemic stroke and could be used to evaluate therapeutic interventions. This study was approved by the Animal Ethics Committee of the Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences (approval No. D2021-03-16-1) on March 16, 2021., Competing Interests: None

The schematic diagram is an indispensable part of research article in life science，which can effectively and intuitively show the specific content of the article with simple composition. As an intuitive expression of the interdisciplinary subject at the early stage, the schematic diagram in the literature has gained an all-round improvement in the quality along with the deve-lopment of computer technology and modern drawing tools. In contrast，the level of the schematic diagram appears to be lagged behind in the field of acupuncture research papers. In order to improve the drawing level of this field, we took the Five Shu-points of Hand and Foot Jueyin Meridian as an example, and drew some vector diagrams of their anatomical structures including the body surface, skeleton, nerves, arteries and veins by using the Adobe Illustrator image software, through which we sum up a simple and easy-to-learn process including application skills and key points needing attention. We hope these methods can play a role in the acupuncture research in the future.

Objective: To investigate the effect of acupuncture in different tissue structures on deqi and the electromyography of acupoint area., Methods: Twenty healthy subjects, respectively accepted 4 kinds of needling stimulation, i.e. stimulating skin at Zusanli (ST36), stimulating ST36 with and without skin anesthesia using compound lidocaine cream, and stimulating at Dubi (ST35) without skin anesthesia. Deqi sensation of the acupuncturist and subjects were measured according to MGH Acupuncture Sensation Scale (MASS) during needling, and the myoelectricity around the acupoints was recorded simultaneously. The occurrence rate and intensity of the different deqi sensations, the relationship between the acupuncturist's and subjects' deqi sensations, and the integrated electromyogram (iEMG) were analyzed., Results: Sharp pain and tingling were the main sensations during skin needling at ST36. Fullness, dull pain, soreness and acupuncturist's tightness were the main sensations during needling with or without skin anesthesia at ST36. Fullness was the main sensation during needling at ST35, while the intensity was lower than that during needling at ST36. A positive correlation in the intensity was found between subjects' fullness and acupuncturist's tightness during needling with or without skin anesthesia at ST36. The subjects' fullness appeared earlier about 5 seconds than acupuncturist's tightness. The iEMGs during subjects' fullness and acupuncturist's tightness were 2-3 times of that before needling., Conclusion: Deqi sensations such as subjects' fullness, dull pain, soreness and acupuncturist's tightness are mainly related to the activity of the muscles under the acupoints. Subjects' fullness and acupuncturist's tightness always appear together. Acupuncturist's tightness may be mediated by the muscle stretch reflex induced by needling stimulation.

Scalp acupuncture is widely used in clinical practice, and there is still a lack of systematic studies on its nerve pathways and mechanism of action. Scalp acupoints are innervated by the trigeminal nerve which is also involved in the regulation of the leptomeninges and related arterioles nourishing the cerebral cortex. Animal experiments and human trials have shown that scalp acupuncture can exert an effect through the shortcut between the axon reflexes from the primary neurons in the trigeminal ganglion (its axon branches may separately innervate scalp acupoints and the leptomeninges directly regulating nutrient and active substances in brain tissue) and the secondary neurons of the trigeminal nucleus caudalis (head and face acupoints interact with afferents of brain tissue through presynaptic dorsal root reflex and postsynaptic neurogenic responses and convergence), which may have regulatory and therapeutic effects on intracranial tissue.

Objective: To provide a new method for investigating the histological characteristics of acupoints by obser-ving the microstructure of the lymphatic vessels in the skin tissue of "Taichong" (LR3) and "Yongquan" (KI1) regions., Methods: Six male SD rats were used in the present study. The skin tissue of LR3 and KI1 from the hind foot were taken following transcardial perfusion with 4% paraformaldehyde. The skin tissues were cut into sagittal sections with a freezing microtome and stained by fluorescent immunohistochemistry with lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), calcitonin gene-related peptide (CGRP), and phalloidin for displaying the lymphatic vessels, nerve fibers, and blood vessels, separately. The samples were viewed and recorded using fluorescent microscope and laser scanning confocal microscope., Results: In the skin tissue of LR3 and KI1 regions, the lymphatic vessels, nerve fibers, and blood vessels were labeled with LYVE-1, CGRP and phalloidin, respectively. The lymphatic capillaries were found to start from the enlarged blind end and distribute in the dermis and subcutaneous tissues with various forms, crisscrossing. Abundant blood capillaries at various thickness distributed around the lymphatic capillaries in a parallel or crossed pattern, intermingled with free nerve fibers., Conclusion: The lymphatic capillaries, blood capillaries and nerve fibers extensively distribute in the skin tissues of LR3 and KI1 regions in rats, suggesting an involvement of the immunomodulation in the effects of acupuncture in pathological conditions, despite being not limited to the acupoint regions in the distribution of lymphatic capillaries.

Histological pictures are important parts of medical research articles, and a good histological picture not only visualizes the content of the article, but also makes it easier for readers to understand. With the rapid development of microscopic technology and image processing technology, journals have higher requirements for the quality of histological pictures and more strict requirements for the editing and annotation of pictures. Based on an analysis of the current status of histological pictures in the articles of Acupuncture Research , this article proposes our suggestions and Methods for rational use of histological pictures, so as to provide a reference for improving the quality of histological pictures in the articles published in Acupuncture Research .

Objective: To collect literatures on the application of neural tracing technique in experimental acupuncture research, and summarize its application status in acupoints, meridians and Zang-fu organs., Methods: We collected papers published from databases of CNKI (1979-2017), Wan-Fang (1990-2017), VIP (1989-2017) and PubMed(1997-2017)by using keywords of "neural tracing technique" "neuroanatomic tracing" "neural tracers" and "acupuncture" "electroacupuncture" "auricular acupuncture" "eye acupuncture" "meridians" "acupuncture points" "acupoint injection", and made a summary about the current state of application of neural tracing technique in the fields of acupoint, meridian and Zang-fu organs (viscera)., Results: A total of 94 articles were collected, the most commonly used neural tracers were horseradish peroxidase and cholera toxin subunit B. The experimental animals used were rat, rabbit, cat, monkey, etc., and injection site was acupoint. After the injection of neural tracers, the survival time of animals was range from 1 day to 12 weeks, and the labelled tissues included neurons and nerve fibers of the sensory, motor, and autonomic systems. The outcomes of neural labeling mainly revealed the segmental pattern, neuroanatomical connection (neural pathways/circuits) and chemical features (shown by immunohistochemical staining) of neurons and nerve fibers innervating both the acupoints and visceral organs, suggesting their involvement in the effect of acupuncture and moxibustion treatment., Conclusion: This application of neural tracing technology help us understand the under-lying mechanisms of acupuncture and moxibustion interventions from different perspectives of neural pathways/circuits and related chemical properties, which also lays a greater role for this technology in future experimental acupuncture research.

Objective: To investigate the expression of serotonin (5-HT) in local tissue of different acupoint regions at the hind limbs of rats., Methods: A total of 6 male SD rats were used in the present study. The local tissues of "Neiting"(ST44), "Zusanli"(ST36) and "Futu"(ST32) at the hindlimbs were dissected after transcardiac perfusion with fixative solution containing 4% paraformaldehyde, phosphate buffer, etc., fixed again in 4% paraformaldehyde and cut into sections (at 20 µm thick). Then, the tissue sections were subjective into immunofluorescence stain for displaying 5-HT positive cells and calcitonin gene-related peptide (CGRP) -positive fibers, vessel-like structure (labelled with phalloidin) and cellular nucleus (labelled with DAPI), separately. After that, the tissue samples were observed and recorded using a laser confocal microscope., Results: The 5-HT labeled cells presented flat or round form in the local tissues of the 3 acupoint regions. These cells were mainly located in the dermis and subcutaneous tissue, and concentrated around the vessel-like structure and CGRP-positive nerve fibers. The number of cutaneous 5-HT positive cells was most in ST44 (156.6±12.1), and fewer in ST36 (83.5±18.2)and ST32(53.3±5.2)in turn., Conclusion: 5-HT-positive cell is an important member in local tissue of acupoints (ST44, ST36 and ST32), and varies in number according to their locations, suggesting an involvement of different densities of 5-HT-positive cells in different levels of regulatory effects of acupuncture stimulation of these acupoints.

Objective: To explore the effect of moxa-stick moxibustion and joss-stick moxibustion at "Guanyuan" (CV4) on the activity of mast cells in the small intestine tissue in rats., Methods: Twelve male SD rats were randomly divided into control, joss-stick moxibustion and moxa-stick moxibustion groups ( n =4 rats in each group). Joss-stick or moxa-stick moxibustion was applied to CV4 for 10 min. After moxibustion, the skin temperature of the CV4 region was measured immediately with a thermometer. The mast cells and nerve fibers in the small intestine tissue were displayed by immunofluorescence histochemistry., Results: Compared with the control group, the skin temperature of the CV4 region in both the joss-stick and the moxa-stick groups were significantly increased ( P <0.05), while the skin temperature of the moxa-stick group was significantly higher than that in the joss-stick group ( P <0.05). There were a large number of tryptase-positive mast cells in the small intestine of rats, some of which were co-expressed with lysosomal-associated membrane protein 1, displaying an activated state. The average numbers of mast cells in the control, joss-stick and moxa-stick groups were 9.2±3.6, 10.8±5.3 and 17.1±6.3, respectively, being significantly higher in the moxa-stick group than in the control and joss-stick groups ( P <0.05). In addition, calcitonin gene-related peptide(CGRP) and neuropeptide Y(NPY) positive nerve fibers were found around the mast cells in the small intestinal tissues., Conclusion: Moxa-stick moxibustion gives rise a higher temperature at CV4 to activate mast cells surrounded by CGRP and NPY positive nerve fibers in the small intestine tissue in rats, suggesting an involvement of the sensory and sympathetic nervous system in the activation of intestinal mast cells possibly by way of somatic sympathetic reflex.

Acupuncture sensation, as one of the essential signs of deqi (arrival of qi ), is closely associated with curative effect. With systematically reviewing the literature regarding relationship between acupuncture sensations of deqi and different organizational structures of acupoint area (skin, connective tissue, muscles, nerves and blood vessels), it is believed that acupuncture sensation of deqi is the product of various organizational structures in acupoint area, which is closely related to the nervous system. The deqi sensations sensed by the hands of acupuncturists, which is called sense of needle stagnation, maybe caused by the contraction of muscles in the acupoint area during the process of needle manipulation. By system review, this paper puts forward a new research idea to explore the role of different manipulations of needling in generating the sense of qi -generating needle based on different acupoint structure and brain function response system, which could provide some reference for clarifying the scientific mechanism and clinical application of acupuncture sensations of deqi .

The NIH-funded "Stimulating Peripheral Activity to Relieve Conditions (SPARC)" program has been initiated in Octomber 2016, aiming at developing high resolution neural circuit maps and next generation neural modulation devices. This program has brought great stimulus to acupuncturists and acupuncture researchers both at home and abroad. Is the SPARC program a driving force or a challenge of acupuncture research? In the present study, we introduced the SPARC program and compared it with current acupuncture research. The first step of SPARC is to better map neural circuits associated with disease on the anatomical level so as to identify the best points for intervention, and to decode the neural language at these intervention points for developing a dictionary of patterns associated with health and disease states on the signaling level. Similarly, our acupuncture research also focuses on revealing the neural encoding of acupuncture stimulation and its effect on visceral function, seeking suitable stimulation parameters to regulate the abnormal visceral activity precisely. Therefore, the common point of SPARC program and acupuncture research is the scientific basis of peripheral somatic neuronal regulation, and their difference is that acupuncture regulates the visceral function through multiple neural circuits and neural feedbacks by stimulating the sensitized points or acupoints, achieving homeostasis at last. Acupuncture-induced regulation effect is limited and the therapy is safe. Whereas, "stimulating periphe-ral activity (SPA)" can regulate the visceral organs precisely but without neural feedback. Inevitably, SPA will produce tolerance or side effects. Therefore, there is still much work to be done in terms of the initiation of trigger stimulation and the feedback inhibition of target organ effects. The SPARC program is definitely a powerful force in revealing the mechanisms by which acupuncture works.

Objective: To try to re-map an acupoint atlas in vector mode in the experimental rat by using a new-generation drawing tool., Methods: A total of 5 SD rats were used in the present study. In reference to the current acupoint locations and anatomical structure of rats as well as those of the human body, an acupoint atlas having a stereoscopic mode was re-mapped by using Adobe photoshop/illustrator CS6 imaging processing and drawing system., Results: According to the skeletal structure and body surface landmarks, an acupoint atlas consisting of Shuigou (GV26), Baihui (GV20), Tianmen (i.e. Cuanzhu, BL2), Erjian (MA-H6), Dazhui (GV14), Feishu (BL13), Xinshu (BL15), Geshu (BL17), Jizhong (GV6), Pishu (BL20), Shenshu (BL23), Houhui (SI3), Huantiao (GB30), Houhai, Yanglingquan (GB34), Housanli (ST36), Zhaohai (KI6), Sanyinjiao (SP6), Genduan point, Shenmai (BL62), Taichong (LR3), Zhijian (foot), Yongquan (KI1), Guanyuan (CV4), Xiqian, Weijian, Shenque (CV8), Zhongwan (CV12), Qiansanli (LI10), Waiguan (SJ5), Neiguan (PC6), Quchi (CV6), Zhoujie (EX-UE1), Hegu (LI4), Zhijian (hand), Houxi (SI3), Shenmen (HT7), Taiyuan (LU9), Shaohai (HT3), Chize (LU5), Danzhong (CV17), and Chengjiang (CV24) which have been positioned in plane graph mode by Professor HUA Xing-bang and colleagues in 1991. The newly re-mapped acupoint atlas displayed more clearly in the anatomic locations relevant to the traditional one., Conclusion: A new acupoint atlas with 3 dimension image mode is accomplished in the rat, being more convenient and applicable for researchers to edit the relevant graph materials in paper writing, and playing a possibly useful guidance for the standardization of acupoint selection in experimental acupuncture researches.

Laser scanning confocal microscope (LSCM) has been used in the field of morphological research of acupuncture and moxibustion for more than 20 years. It is one of the important tools for revealing the structure of acupoints and the effect of acupuncture from histological perspective. With the help of technical advantages of LSCM, the quality of morphological research of acupuncture and moxibustion has been greatly improved, helping us gain a deeper understanding about the structure of acupoints and meridians as well as histochemical changes induced by acupuncture/moxibustion intervention. In order to promote the application of LSCM in acupuncture and moxibustion, we simply reviewed some recent studies in this field and combined them with our experience, trying to provide some technical suggestions. We expect that the technique of LSCM could be integrated into more experiments in acupuncture medicine to provide more powerful morphological evidence for exploring the underlying mechanisms of acupuncture and moxibution therapies.

Objective: To explore the neuroanatomical basis of acupoint-visceral correlation by studying the distribution of the neurons associated with acupoint "Shenshu" (BL 23) area and adrenal gland in rats., Methods: AF 488-CTB and AF 594-CTB were injected into the left side of BL 23 area and adrenal gland in the same rat respectively. Three days after injection, the dorsal root ganglions (DRG), sympathetic chain, and spinal cord were dissected out from the perfused rats. The neuronal labeling with AF 488/594-CTB was directly observed on the sections under a fluorescent microscope or a laser scanning confocal microscope., Results: All neural labeling was observed in the injection side. The sensory neurons associated with both acupoint BL 23 and adrenal gland distributed from thoracic (T) 10 to lumbar (L) 2 DRG with high concentration in T 12-T 13 and T 11-T 12, respectively, in which some of them were simultaneously labeled with both AF 488/594-CTB and located in T 12-L 1 DRG. For the sympathetic innervation, the postganglionic neurons correlated with BL 23 and adrenal gland were labeled with AF 488/594-CTB separately in the sympathetic chain at the lumbar segments, while the labeled preganglionic neurons were only observed at the lateral horn of T 11-T 13 spinal segments in the cases of adrenal gland. In addition, the labeled motor neurons were mainly detected in the spinal ventral horn at cervical (C) 7-C 8 and T 11-L 1 segments., Conclusion: These results indicate that there are segmental correlation between BL 23 and adrenal gland on the sensory and sympathetic innervations, and this correlation might be a neural pathway for modulating the function role of adrenal gland through BL 23 needling.

The anatomical structure of acupuncture points is the carrier for needling stimulation induced neurobiological effects. Although researchers have never stopped investigating its structure and experienced different stages from macroscopic to microcosmic morphological material basis, our understanding still largely lags behind the requirements of the times. In the present paper, we review development of researches on acupuncture points in recent decades from 1) macroscopic anatomical structure including skin, bones, muscles, nerves, blood vessels, etc.; 2) macro-microcosmic structure as the thickness of skin and muscles, distribution of blood vessels and nerve fibers, and innervation; 3) microstructure including cell categories (mast cells, fibroblasts, macrophages, etc.), peptidergic nerve fibers, various receptors, chemical substances, and their relationship with the brain and immune-endocrine system (cutaneous-neuro-immune-endocrine-mental biological communication), etc. These research outcomes will not only help us demonstrate the acupoint's structure better at the level of the body surface and regional anatomy, but also, at the microstructural level, reveal different kinds of cells and their chemical compositions in its structure as well as their relationship with the regulatory system of the whole body. From the perspective of the cutaneous and systemic neuro-immuno-endocrine networks, it undoubtedly prompts us to profoundly explore the underlying biological mechanisms of acupuncture. To observe the regional mutual connection and interaction of different kinds of cells and their chemical mediators and molecules in the acupuncture point will improve our understanding about the nature of acupuncture points from the static to the dynamic point of view. This might be a new approach for us to further reveal the functional roles of acupuncture points.

Objective: To investigate the microstructure (blood vessels and nerve fibers) of the skin tissue in "Taichong" (LR 3) region for reveling morphological characteristics of acupoint., Methods: Five SD rats were used in the present study. The skin tissue in the region of acupoint LR 3 was taken from the dorsum of hind foot following transcardial perfusion with 4% paraformaldehyde. Then, the skin samples were sagittally or horizontally cut into sections (20 μm or 40 μm in the thickness) to be stained with Phalloidin and calcitonin gene related peptide (CGRP) by using fluorescent histochemistry and immunohistochemistry. The labeled vascular structure and nerve fibers were observed and recorded using fluorescent microscope and laser scanning confocal microscope., Results: In the skin tissue of LR 3, different types of blood vessels labeled by phalliodin, including capillaries and glomera mainly distributing in the superficial layer of the dermis, and thicker blood vessels and their sub-branches mainly existing in the deeper layer of the dermis and the subcutaneous layer, were found. In addition, CGRP positive nerve fibers were found to run parallel to the thin blood vessels or to gather around the thicker blood vessels. From the subcutaneous la-yer to the epidermis, blood vessels and nerve fibers coexisted and formed a stereo-network structure., Conclusions: In the skin of LR 3 area, there exists a stereo-network structure consisting of different types of blood vessels and nerve fibers. Although this structure is not specifically associated with acupoint area alone, this result may provide a new sight to further understand the microstructure of acupoint.

Objective: To investigate the distribution of substance P (SP)-positive nerve fibers in local skin tissues of the five shu -points of the Pericardium Meridian in rats for revealing the differential innervations of the five acupoints., Methods: Six adult male SD rats were used in the present study. Under deep anesthesia, the rats received transcardiac perfusion with 4% polyformaldehyde+phosphate buffered solution, followed by dissecting the local skin tissues from the sites corresponding to five shu -points "Zhongchong" (PC 9), "Laogong" (PC 8), "Daling" (PC 7), "Jianshi" (PC 5), and "Quze" (PC 3) in the human body. The tissues were sagittally cut into sections (20 μm) using a freezing microtome, followed by fluorescent immunohistochemi-cal and histochemical staining with SP, phalloidin and DAPI, respectively. The distribution of SP-positive fibers were observed under fluorescent microscope and laser confocal microscope., Results: In general, SP expressed on the thin sensory fibers in the skin tissue. SP-positive nerve fibers distributed in a free single style in the epidermis and dermis, and gathered together to form a bundle in the subcutaneous layer. After counting the number and length of free single fibers in the epidermis and dermis of each of the five shu -points, we found that no significant differences existed in the density between the PC 9 and PC 8 regions, as well as among the PC 7, PC 5, and PC 3 regions ( P >0.05). In contrast, the density of SP-positive nerve fibers in the former two acupoints (PC 9 and PC 8) was significantly higher than that of anyone of the latter three acupoints ( P <0.01). In addition, SP positive nerve fibers mainly ran in parallel to the vessel-like structure., Conclusions: The local skin tissues of acupoint PC 9, PC 8, PC 7, PC 5, and PC 3 of the Pericardium Meridian express SP-positive fibers, which presents a decreasing tendency in the density from the distal to the proximal part of the forelimb, reflecting a relative specificity of the innervations of the five shu -points.