Role In Acupuncture Analgesia Research Articles

Peripheral Rho-associated protein kinase activation mediates acupuncture analgesia

BackgroundAcupuncture has proven effective for various types of pain and peripheral molecular signals around acupuncture-treated areas have been suggested to contribute to the analgesic effects of acupuncture; however, the underlying mechanism from these peripheral molecular signals to central ones remains unclear. We investigated whether peripheral Rho-associated protein kinase (ROCK) activation induced by acupuncture treatment mediates acupuncture analgesia. We also investigated the relationship between ROCK activation and extracellular signal-regulated kinase (ERK), which has previously been proven to mediate acupuncture analgesia and other related molecular changes during acupuncture. MethodsAcupuncture was treated at the bilateral GB34 acupoints of C57BL/6 mice, after which changes in ROCK activation and the location of its expression in the skin were analyzed. To verify the role of ROCK in acupuncture analgesia, we administrated ROCK inhibitor Y-27632 (0.3 μg/ul) into the skin before acupuncture treatment with formalin and complete Freund adjuvant (CFA) induced pain models, then the nociceptive responses were analyzed. ResultsAcupuncture treatment produced ROCK2 activation in the skin after 30 and 60 minutes, and the histological analyses revealed that ROCK2 was activated in the fibroblast of the dermis. The acupuncture-induced ROCK2 expression was significantly attenuated by the ERK inhibitor, whereas phospho-ERK expression was not inhibited by ROCK inhibitor. In both the formalin- and CFA-induced mouse pain models, acupuncture analgesia was blocked by ROCK inhibitor administration. ConclusionAcupuncture treatment-induced ROCK2 expression is a downstream effector of phospho-ERK in the skin and plays a crucial role in acupuncture analgesia.

The role of purinergic signaling in acupuncture-mediated relief of neuropathic and inflammatory pain.

Acupuncture is a traditional medicinal practice in China that has been increasingly recognized in other countries in recent decades. Notably, several reports have demonstrated that acupuncture can effectively aid in pain management. However, the analgesic mechanisms through which acupuncture provides such benefits remain poorly understood. Purinergic signaling, which is mediated by purine nucleotides and purinergic receptors, has been proposed to play a central role in acupuncture analgesia. On the one hand, acupuncture affects the transmission of nociception by increasing adenosine triphosphate dephosphorylation and thereby decreasing downstream P2X3, P2X4, and P2X7 receptors signaling activity, regulating the levels of inflammatory factors, neurotrophic factors, and synapsin I. On the other hand, acupuncture exerts analgesic effects by promoting the production of adenosine, enhancing the expression of downstream adenosine A1 and A2A receptors, and regulating downstream inflammatory factors or synaptic plasticity. Together, this systematic overview of the field provides a sound, evidence-based foundation for future research focused on the application of acupuncture as a means of relieving pain.

Electroacupuncture Exerts Analgesic Effects by Restoring Hyperactivity via Cannabinoid Type 1 Receptors in the Anterior Cingulate Cortex in Chronic Inflammatory Pain.

As one of the commonly used therapies for pain-related diseases in clinical practice, electroacupuncture (EA) has been proven to be effective. In chronic pain, neurons in the anterior cingulate cortex (ACC) have been reported to be hyperactive, while the mechanism by which cannabinoid type 1 receptors (CB1Rs) in the ACC are involved in EA-mediated analgesic mechanisms remains to be elucidated. In this study, we investigated the potential central mechanism of EA analgesia. A combination of techniques was used to detect the expression and function of CB1R, including quantitative real-time PCR (q-PCR), western blot (WB), immunofluorescence (IF), enzyme-linked immunosorbent assay (ELISA), and in vivo multichannel optical fibre recording, and neuronal activity was examined by in vivo two-photon imaging and in vivo electrophysiological recording. We found that the hyperactivity of pyramidal neurons in the ACC during chronic inflammatory pain is associated with impairment of the endocannabinoid system. EA at the Zusanli acupoint (ST36) can reduce the hyperactivity of pyramidal neurons and exert analgesic effects by increasing the endocannabinoid ligands anandamide (AEA), 2-arachidonoylglycerol (2-AG) and CB1R. More importantly, CB1R in the ACC is one of the necessary conditions for the EA-mediated analgesia effect, which may be related to the negative regulation of the N-methyl-D-aspartate receptor (NMDAR) by the activation of CB1R downregulating NR1 subunits of NMDAR (NR1) via histidine triad nucleotide-binding protein 1 (HINT1). Our study suggested that the endocannabinoid system in the ACC plays an important role in acupuncture analgesia and provides evidence for a central mechanism of EA-mediated analgesia.

The real-time detection of acupuncture-induced extracellular ATP mobilization in acupoints and exploration of its role in acupuncture analgesia.

Our and in vitro studies had confirmed that mechanosensitive ATP release and accumulation in acupoints was elicited by acupuncture (AP), which might be a pivotal step for triggering AP analgesia. But to date, the dynamics of extracellular ATP (eATP) in the interstitial space during AP process was poorly known, mainly due to the low temporal resolution of the current detection approach. This study attempted to capture rapid eATP signals in vivo in the process of needling, and further explored the role of this eATP mobilization in initiating AP analgesic effect. Ipsilateral 20-min needling was applied on Zusanli acupoint (ST36) of complete Freund's adjuvant (CFA)-induced ankle arthritis rats. Pain thresholds were assessed in injured-side hindpaws. eATP in the interstitial space was microdialyzed and real-time quantified by luciferin-luciferase assay at 1-min interval with the aid of the microfluid chip. We revealed in behavioral tests that modulation of eATP levels in ST36 influenced AP analgesic effect on ankle arthritis. A transient eATP accumulation was induced by needling that started to mobilize at 4min, climbed to the peak of 11.21nM within 3.25min and gradually recovered. Such AP-induced eATP mobilization was significantly impacted by ankle inflammation, needling depth, needle manipulation, and the presence of local ecto-nucleotidases. This work reveals that needling elicits a transient eATP mobilization in acupoints, which contributes to initiating AP analgesia. This study will help us better understand the peripheral mechanism of AP analgesia and guide clinicians to optimize the needle manipulations to improve AP efficacy.

Cellular Reorganization Plays a Vital Role in Acupuncture Analgesia.

Background: Acupuncture has a long history of relieving many forms of pain. However, many of acupuncture's mechanisms are still unknown and/or misunderstood. Objective: This review looks at past research on many different methods and targets of study related to acupuncture. The main focus is upon the importance of connective-tissue planes in and around acupuncture points. Method: Relevant articles from journals as well as books on the topic were searched manually for information related to the topic. Results: Various studies offered different (and sometimes interrelated) mechanisms for how acupuncture needling results in analgesia among other effects. Emerging evidence, however, has shown the increasing importance of extracellular matrix rearrangements that result in lower mechanical stress states of surrounding tissues. This leads to lower constant stimulation of regional mechanoreceptors, in turn, reducing chronic pain and discomfort. Conclusions: The extracellular matrix has emerged as an important area of study on the effects of acupuncture needling.

Contribution of adenosine to the increase in skeletal muscle blood flow caused by manual acupuncture in rats.

Adenosine is believed to play an important role in local acupuncture analgesia. The aim of this study was to investigate the contribution of adenosine to the increase in skeletal muscle blood flow (MBF) caused by manual acupuncture (MA). Thirty-two male Sprague-Dawley rats (310-360 g) were anaesthetised and divided into four equal groups (n=8 each): Saline, Saline+MA, Theophylline, and Theophylline+MA. In the two MA groups, the sparrow-pecking MA technique was applied at 30 repetitions per min for 1 min to a depth of 15-18 mm using a stainless steel acupuncture needle (0.20×40 mm). The stimulus point was located on the right tibialis anterior (TA) muscle 7-8 mm below the knee. Animals in the two theophylline groups were intra-arterially injected with 8-(p-sulphophenyl) theophylline, a non-selective adenosine receptor antagonist, at a dose of 30 mg/kg before MA. Animals in the two saline groups received control saline. Fluorescent microspheres (15 µm in diameter, yellow-green fluorescent) were used for MBF measurement in all four groups. MA of the TA muscle significantly increased MBF (Saline+MA vs Saline: p=0.001; Saline+MA vs Theophylline: p=0.008). Pre-treatment with theophylline appeared to inhibit this increase (Theophylline vs Theophylline+MA; p=1.000). MBF in the Theophylline+MA group was 43% lower than in the Saline+MA group, although this was not significantly different (p=0.104). The results suggest that adenosine leads to an increase in MBF caused by MA. Adenosine may play a role in acupuncture analgesia by washing out algesic substances. Further studies are needed in order to elucidate the precise mechanism.

Endogenous Anandamide and Cannabinoid Receptor-2 Contribute to Electroacupuncture Analgesia in Rats

Acupuncture is widely used clinically to treat acute and chronic pain conditions, but the mechanisms underlying its effect are not fully understood. Although endocannabinoids are involved in modulation of nociception in animal models and in humans, their role in acupuncture analgesia has not been assessed. In this report, we determined the effect of electroacupuncture (EA) on the level of anandamide in the skin tissue and the role of cannabinoid CB1 and CB2 receptors in the analgesic effect of EA in an animal model of inflammatory pain. Inflammatory pain was induced by local injection of complete Freund's adjuvant (CFA) into the hind paw of rats. Thermal hyperalgesia was tested with a radiant heat stimulus, and mechanical allodynia was quantified with von Frey filaments. The anandamide concentration in the skin tissue was measured by using high-performance liquid chromatography. EA, applied to GB30 and GB34, at 2 and 100Hz significantly reduced thermal hyperalgesia and mechanical allodynia induced by CFA injection. Compared with the sham group, EA significantly increased the anandamide level in the inflamed skin tissue. Local pretreatment with a specific CB2 receptor antagonist, AM630, significantly attenuated the antinociceptive effect of EA. However, the effect of EA was not significantly altered by AM251, a selective CB1 receptor antagonist. These findings suggest that EA potentiates the local release of endogenous anandamide from inflamed tissues. Activation of peripheral CB2 receptors contributes to the analgesic effect of EA on inflammatory pain. This study shows that electroacupuncture increases the anandamide level in inflammatory skin tissues, and CB2 receptors contribute to the analgesic effect of electroacupuncture in a rat model of inflammatory pain. This information improves our understanding of the mechanisms involved in the analgesic effect of acupuncture.

Disinhibitory Involvement of the Anterior Cingulate Cortex in the Descending Antinociceptive Effect Induced by Electroacupuncture Stimulation in Rats

The present study was conducted to clarify the role of the anterior cingulate cortex (ACCX) in acupuncture analgesia. Experiments were performed on 35 female Wistar albino rats weighing about 300 g. Single unit recordings were made from ACCX neurons with a tungsten microelectrode. Descending ACCX neurons were identified by antidromic activation from electrical shocks applied to the ventral part of the ipsilateral PAG through a concentric needle electrode. Cathodal electroacupuncture stimulation of Ho-Ku (0.1 ms in duration, 45 Hz) for 15 min was done by inserting stainless steel needles bilaterally. An anodal silver-plate electrode (30 mm x 30 mm) was placed on the center of the abdomen. Naloxone (1.0 mg/kg, i.v.) was used to test whether changes of ACCX activities were induced by the endogenous opioid system. Data were collected from a total of 73 ACCX neurons. Forty-seven neurons had descending projection to the PAG, and the other 26 had no projections to the PAG. A majority of descending ACCX neurons were inhibited by electroacupuncture stimulation. By contrast, non-projection ACCX neurons were mainly unaffected by electroacupuncture. Naloxone did not reverse acupuncture effects on the changes of ACCX neuronal activities. Acupuncture stimulation had predominantly inhibitory effects on the activities of descending ACCX neurons. Since the functional connection between ACCX and PAG is inhibitory, electroacupuncture caused disinhibition of PAG neurons, whose activity is closely related to descending antinociception to the spinal cord. This disinhibitory effect elicited by acupuncture stimulation is thought to play a significant role in acupuncture analgesia.

Effect of hypothalamic supraoptic nucleus on acupuncture analgesia in the rat

Hypothalamic supraoptic nucleus (SON) has been demonstrated to involve in pain modulation. Acupuncture analgesia is a very useful clinical skill for pain relief, which has over 2500-year history in China. The present study investigated the effect of SON on acupuncture analgesia in the rat. Electrical stimulation of the SON or microinjection of a small dose l-glutamate sodium into the SON enhanced acupuncture analgesia in a dose-dependent manner, while cauterization of the SON weakened acupuncture analgesia. Pituitary removal did not influence the effect of l-glutamate sodium that enhanced acupuncture analgesia in the SON. The data suggested that the neurons and not the nerve fibers in the SON played an important role in acupuncture analgesia, which effect might be through the central nervous system rather than the hypothalamo-neurohypophyseal system.

Through central arginine vasopressin, not oxytocin and endogenous opiate peptides, glutamate sodium induces hypothalamic paraventricular nucleus enhancing acupuncture analgesia in the rat

Our previous study proved that the hypothalamic paraventricular nucleus (PVH) plays an important role in acupuncture analgesia. The neuropeptides involving in the PVH regulation of acupuncture analgesia was investigated in the rat. The changes of pain threshold, which was induced by electrical acupuncture of “Zusanli” points (St. 36), were measured as acupuncture analgesia. Microinjection of l-glutamate sodium into the PVH, which only excites the PVH neurons, could dose-dependently enhance the acupuncture analgesia, but microinjection of l-glutamate sodium into the area nearby the PVH did not alter acupuncture analgesia. Removing pituitary did not influence this effect of l-glutamate sodium. Microinjection of l-glutamate sodium into the PVH only increased the arginine vasopressin (AVP), not oxytocin (OXT), leucine enkephaline (L-Ek), β-endorphine (β-Ep) and dynorphinA 1–13 (DynA 1–13) concentrations in the PVH perfuse liquid using radioimmunoassay. Intraventricular injection of anti-arginine vasopressin serum (AAVPS) could completely reverse the effect of microinjection of l-glutamate sodium into the PVH enhancing acupuncture analgesia. Intraventricular injection of naloxone, one opiate peptide antagonist, partly attenuated this effect of l-glutamate sodium, and intraventricular of anti-oxytocin serum (AOXTS) did not change this effect of l-glutamate sodium. The results suggested that l-glutamate sodium induces the PVH enhancing acupuncture analgesia only through AVP, not OXT and endogenous opiate peptides in central nervous system.

Only arginine vasopressin, not oxytocin and endogenous opiate peptides, in hypothalamic paraventricular nucleus play a role in acupuncture analgesia in the rat

Our previous study proved that hypothalamic paraventricular nucleus (PVH) plays an important role in acupuncture analgesia. The effect of acupuncture on the concentrations of arginine vasopressin (AVP), oxytocin (OXT), leucine-enkephaline (L-Ek), β-endorphin (β-Ep) and dynorphinA 1–13 (DynA 1–13) was investigated in rat PVH. Electrical acupuncture of “Zusanli” points (St. 36) 30 min increased the AVP, not OXT, L-Ek, β-Ep and DynA 1–13 concentrations in PVH tissue using micropunch and radioimmunoassay, which showed a negative relationship between the pain threshold and AVP concentrations in PVH tissue. Electrical acupuncture could elevate the AVP concentrations in PVH perfuse liquid during acupuncture, and then reduce the AVP concentrations in PVH perfuse liquid after acupuncture. But no change in OXT, L-Ek, β-Ep and DynA 1–13 concentrations was detected in PVH perfuse liquid. Electrical acupuncture decreased the number of AVP, not OXT, L-Ek, β-Ep and DynA 1–13 immunoreactive cells in PVH using immunocytochemistry. The results suggested that only AVP, not OXT and endogenous opiate peptides in PVH involved acupuncture analgesia in the rat.

Role of opioid peptides of rat's nucleus reticularis paragigantocellularis lateralis (RPGL) in acupuncture analgesia.

The present study was to investigate the role of the RPGL and its endogenous opioid peptides in acupuncture analgesia (AA) using techniques of brain stimulation and lesion, microinjection, push-pull perfusion and radioimmunoassay (RIA). The results showed that electrical stimulation of the RPGL could increase the pain threshold and enhance the effect of AA, whereas lesion of the RPGL reduce the effect of AA. Microinjection of naloxone (5 micrograms/0.5ul/2min) into the RPGL could partially reverse the effect of AA and the reversal effect of naloxone was dose-dependent. The release of leu-enkephalin (LEK) and B-endorphin (B-EP) from the RPGL in the electrical acupuncture (EA) group was significantly higher than that in the control group (P < 0.05). There were positive correlations between the changes of release of LEK, B-EP and the increase of pain threshold. The results mentioned above imply that the RPGL plays an important role in AA. The activation of the RPGL and the endogenous opioid peptides within it produce an advantageous effect on AA.

Hypothalamic paraventricular nucleus plays a role in acupuncture analgesia through the central nervous system in the rat.

This work investigates the effect of hypothalamic paraventricular nucleus (PVN) on acupuncture analgesia in the rat. Electrical stimulation of PVN or injection of L-glutamate sodium into PVN could enhance the analgesic effect induced by acupuncture Zusanli (St. 36) while the electrical cauterization of PVN is decreased; Removal of the pituitary could not influence the effect of enhancing acupuncture analgesia induced by the injection of L-glutamate sodium into PVN. These results suggest that PVN might play an important role in acupuncture analgesia through central nervous system.

Inhibition of sympathetic nervous system by acupuncture.

The central and peripheral sympathetic activities were measured both physiologically and biochemically in either human subjects or conscious rabbits. Acupuncture reduced NE levels in perfusates of certain brain areas as well as in blood circulation, accompanied with a rise of pain threshold, and changes of certain physiological indices (palm temperature, fingerplethysmogram and pain tolerance threshold) which are related with functions of sympathetic nervous system. These results suggest that the NE neurons of NE ascending dorsal fasciculus has some antagonizing effect on acupuncture analgesic effect, acupuncture inhibits sympathetic activities, and such inhibition plays a favorable role in acupuncture analgesia.

The role of the human caudate nucleus in acupuncture analgesia.

The role of the caudate nucleus in acupuncture analgesia was studied in 17 patients receiving caudate stimulation through chronic implanted electrodes to relieve intractable pain caused by late malignancy. Electrical stimulation of the head of the caudate nucleus provided relief from intractable pain in all 17 patients. The pain and pain tolerance threshold were elevated, the alteration in skin galvanic activity, respiratory movement and fingertip plethysmography elicited by a given painful stimulus were depressed. The analgesia required a period of induction and persisted for some time after cessation of stimulation; it showed no obvious segmental topography. These characteristics are similar to those observed in acupuncture analgesia. The effect of caudate stimulation was similar to that of electric needling in depressing the late component of the somatosensory evoked potentials (SEPs) recorded over the scalp and from the centrum medianum of the thalamus. Evoked potentials could be recorded from the caudate nucleus when an acupuncture point was electrically stimulated. The evoked potential record was a complex wave of positive and negative components, the peak latencies of main components being 100-180 msec for positive wave and 148-332 msec for negative wave components. The present study supports the supposition that the caudate nucleus may play a role in acupuncture analgesia. The possibility that the effect of caudate stimulation is brought on by inhibiting the activity of the medial thalamus is discussed.