Neural mechanism of depressor responses of arterial pressure elicited by acupuncture-like stimulation to a hindlimb in anesthetized rats

Comparison of Hemodynamic Changes During Acupuncture Stimulation in Supine or Sitting Position in Human Subjects

Objective

Position change influences acupuncture-induced heart rate (HR) reduction, which is caused by a somatoautonomic reflex. However, the influences of position on the hemodynamic system-including HR, blood pressure (BP), and cardiac output (CO) during acupuncture-remains unclear. This study comprehensively compared cardiovascular changes induced by acupuncture in human beings supine and sitting positions.

Materials and Methods

Comprehensive measurements were made of 30 healthy male volunteers, including HR, stroke volume (SV), and BP, in a supine posture for 15 minutes. Manual acupuncture stimulation was performed at the left LI-10 point for 1 minute. After at least 1 week, the same protocol was performed with all subjects in a sitting position.

Results

Preacupuncture, there were increases in HR and BP, and decreases in SV and CO in the sitting position, compared with the supine position. Acupuncture stimulation induced HR reduction more when the subjects were in the sitting position, compared with them in the supine position. Acupuncture-induced increase in SV and decrease in diastolic BP were not different in either position. In the sitting position, CO decreased during acupuncture, compared with preacupuncture; this did not occur in the supine position.

Conclusions

The effects of acupuncture on the hemodynamic system changed between the supine and sitting positions in healthy young men. Autonomic nervous-tone influences acupuncture-induced cardiovascular changes through physiologic responses, including the somatoautonomic reflex and the baroreflex.

Case Report: Acupuncture is an effective treatment for olfactory dysfunction in the post COVID-19 condition

Olfactory dysfunction in the post COVID-19 condition reported worldwide are refractory for some patients. For this reason, appropriate treatment is desired. In this article, we describe two cases of olfactory dysfunction in the post COVID-19 condition that was improved by traditional acupuncture treatment. By using the Yingxiang point (LI20), which is said to improve the sense of smell since ancient times, acupuncture treatment was performed 1-2 times a week in two patients about 6 and 7 months after the diagnosis of COVID-19. Acupuncture needles with a body length of 30 mm and a body diameter of 0.16 mm were inserted about 10 mm deep into the skin. We stimulated LI20 of the right and left sides until the patients felt the de qi sensation (acupuncture resonance), and left needles in the points for about 15 min. Immediately after the acupuncture treatment, the symptoms of olfactory dysfunction were alleviated, and the improvement in olfactory dysfunction lasted for 2-4 days. As the number of acupuncture treatments increased, the time until the flareup of olfactory dysfunction was prolonged, and the symptoms tended to decrease. In our experience, the acupuncture treatment was effective in a short period for treating residual olfactory dysfunction of the post COVID-19 condition, suggesting that acupuncture may serve as an adjunct to modern medical treatment, and it may also be a new option for patients who are resistant to Western medical treatment or unable to continue treatment because of side effects. In conclusion, acupuncture may be a new option for patients who are resistant to modern medical treatment or who are unable to continue treatment because of side effects.

Effects of pre-exercise acupuncture stimulation on heart rate response during short-duration exercise

Background

The purpose of the present study was to investigate the effects of bradycardia induced by pre-exercise acupuncture on heart rate responses during short-duration exercise.

Methods

A total of 29 healthy subjects underwent two protocols: protocol 1 assessed the effects of manual acupuncture on heart rate response during rest, and protocol 2 tested the hypothesis that the bradycardic effects induced by pre-exercise acupuncture continue during low- and high-intensity exercise. Their average age, height, weight, and body mass index were 21.2 ± 2.0 years, 167.2 ± 8.8 cm, 63.8 ± 12.8 kg, and 22.7 ± 3.5 kg/m², respectively. In acupuncture stimulations for protocols 1 and 2, an acupuncture needle was inserted into the lower leg and manual acupuncture stimulation was performed at 1 Hz.

Results

In protocol 1 (resting condition), acupuncture stimulation induced a bradycardic response, which continued for 4 min after the cessation of acupuncture stimulation (p < 0.05). In protocol 2, the bradycardic response induced by pre-exercise acupuncture stimulation remained during low-intensity exercise and in the beginning of high-intensity exercise performed immediately after the cessation of acupuncture stimulation (p < 0.05). However, the effects disappeared when post-acupuncture exercise was performed when the heart rate was approximately 140 beats/min during high-intensity exercise. The rating of perceived exertion after exercise differed significantly between the acupuncture stimulation task (7.9 ± 1.6) and no-stimulation task (8.5 ± 2.0) (p = 0.03) only in the low intensity group.

Conclusion

This study may provide new insights into the effect of acupuncture stimulation on psycho-physiological conditions during exercise.

Effects of a Single Session of Acupuncture Treatment on Blood Pressure and Heart Rate Variability in Patients with Mild Hypertension

Objective: The aim of the present study was to compare the effects of acupuncture treatment on arterial blood pressure (BP) and heart rate (HR) in patients with mild hypertension with high sympathetic tone with those of normotensive patients and to examine the effects on cardiac sympathetic nerve activity (CSNA) and vagal activity using heart rate variability (HRV) analysis. Design: Eight male patients with prehypertension or stage I hypertension and eight normotensive age-matched patients were included in this study. All patients had their systolic BP (SBP), diastolic BP (DBP), HR, and HRV measured. In addition, the ratio of low-frequency (LF) to high-frequency (HF) HRV and the power of the HF of the HRV were recorded. The study was conducted at Kansai University of Health Sciences in Japan. Interventions: Each patient underwent a single, 15-min-long acupuncture session. Acupuncture was applied to PC6, LI4, ST36, LR3 on both sides, and GV20. Results: SBP and HR decreased significantly in the hypertensive group during and after acupuncture compared with the baseline SBP and HR (p < 0.05). LF/HF was significantly reduced during acupuncture (p < 0.05), and HF was significantly increased after acupuncture in the hypertensive group (p < 0.05). However, there were no significant changes in LF/HF or HF in the control group. Conclusions: Acupuncture may reduce the BP and HR in patients with mild hypertension. An HRV analysis suggests that acupuncture may suppress the enhanced basal CSNA activity and increase the vagal nerve activity in patients with mild hypertension. Clinical Trial Registration number: UMIN000041249.

Effects of Moxibustion on Stress-Induced Delayed Gastric Emptying via Somatoautonomic Reflex in Rats

Objective: Moxibustion (MOX) is used to treat a wide variety of disorders, including those with gastric symptoms. However, the exact mechanisms underlying the beneficial effects of MOX are unknown. The purpose of this study was to investigate if application of indirect MOX (iMOX) to ST 36 reduces restraint stress (RS)-induced alteration in gastric responses of conscious rats, and if a somatoautonomic reflex mediates gastric emptying (GE). Materials and Methods: One group of rats was fed solid food after 24 hours of fasting. Immediately after food ingestion. These rats were subjected to RS. Ninety minutes after feeding, the rats were euthanized, and their gastric contents were removed to calculate GE. iMOX had been performed at ST 36 bilaterally throughout the stress loading. To investigate if vagal-nerve activity was involved in mediating the stress-induced alterations of GE by iMOX, atropine was intraperitoneally administered to other rats just before initiating RS; bilateral truncal vagotomy had been performed on day 14 before GE measurement. Results: RS delayed GE significantly (42.9 ± 5.8%)in stressed rats, compared to nonstressed rats (68.7 ± 1.8%). iMOX at ST 36 reduced stress-induced inhibition of GE significantly (67.1 ± 2.4%). MOX-mediated reduction of GE disappeared upon atropine injection and vagotomy. Conclusions: RS-induced delayed GE may be ameliorated by iMOX at ST 36. Somatoautonomic, reflex-induced vagal-nerve activity helps mediate the stimulatory effects of iMOX on RS-induced delayed GE. As a complementary and alternative medicine, iMOX may also be advantageous for patients with gastric disorders, such as functional dyspepsia.

Effect of acupuncture on the haemodynamic system in men

BACKGROUND

Acupuncture stimulation decreases heart rate (HR) through somato-autonomic reflexes. However, the mechanisms responsible for other cardiovascular changes induced by acupuncture, such as its effects on stroke volume (SV) and blood pressure (BP), remain obscure.

OBJECTIVE

To evaluate continuously the comprehensive cardiovascular changes occurring during acupuncture.

METHOD

20 healthy men participated in the study. HR, SV and BP were measured in the supine position using electrocardiogram, transthoracic impedance cardiography and continuous non-invasive finger blood pressure, respectively. Manual acupuncture stimulation using a stainless steel needle was performed at LI10 for 60 s after resting periods of approximately 15 min.

RESULTS

HR was reduced and SV increased, in parallel, during the period of acupuncture stimulation (P<0.01, respectively). Diastolic blood pressure (DBP) decreased in the 10 s period of acupuncture stimulation compared with the 120 s pre-stimulation period (P<0.01) and recovered close to the pre-stimulation reading instantly after the transient reduction. No change was observed in cardiac output (CO) derived from HR and SV.

CONCLUSIONS

This study indicates that HR reduction during acupuncture does occur, as previous reports have indicated. SV increased during acupuncture stimulation in parallel with HR reduction and CO was maintained during these changes. Any reduction in DBP caused by acupuncture recovered to baseline, likely due to baroreflexes.

Acupoint dependence of depressor and bradycardic responses elicited by manual acupuncture stimulation in humans

The cardiovascular effects of the autonomic nervous system (ANS) are modulated by inputs from peripheral sensors and other brain regions. However, it currently remains unknown whether the manual acupuncture (MA) stimulation of different acupuncture points evokes different responses by the heart and vasculature, a phenomenon known as "site specificity". Sixty healthy subjects were randomly divided into a control group and MA stimulation groups at the lower leg, ear, abdomen, and forearm. MA was performed at 1 Hz for 2 min. A depressor response was observed only in the lower leg stimulation group, in which mean blood pressure significantly decreased from 83.4 ± 10.1 to 80.9 ± 11.7 mmHg (p < 0.003). A bradycardic response was elicited in all MA stimulation groups. There was no significant differences in the magnitude of the bradycardic response between groups. MA-induced cardiovascular responses, which may be mediated by the modulation of ANS, differ depending on acupuncture points.

Somatosensory regulation of resting muscle blood flow and physical therapy

Somatosensory stimulation can affect skeletal muscle blood flow (MBF) at rest in anesthetized animals via pressor reflex response or antidromic and local vasodilation. Increase in MBF due to reflex pressor response occurs generally in the skeletal muscles of the entire body, while antidromic and local vasodilation are limited to the peripheral stimulation site. Since increased MBF improves several disorders (muscle stiffness, pain, etc.), it is reasonable to further explore the effective use of somatic stimulation in physical therapies, such as massage, acupuncture, anma, and shiatsu or acupressure, in treating skeletal muscle disorders.

Effects of Manual Acupuncture with Sparrow Pecking on Muscle Blood Flow of Normal and Denervated Hindlimb in Rats

Introduction

In clinical practice, it has been thought that acupuncture might serve to wash out pain-generating metabolic end-products by improving blood circulation in muscles. We investigated the effects of manual acupuncture (MA) on muscle blood flow (MBF) of normal and denervated hindlimbs in rats.

Method

Sprague-Dawley rats (n=100) anaesthetised with urethane (1.2g/kg ip) were used. Manual acupuncture with sparrow pecking (SP) at different doses (1, 10 or 30 pecks) was given to the right ventral hindlimb muscles (tibial anterior and extensor digitorum longus muscles) or the right dorsal hindlimb muscles (gastrocnemius, plantaris and soleus muscles). MBF with or without MA was measured using the radiolabelled microsphere technique. The blood pressure was recorded through the right common carotid artery until MBF measurement started. Denervation of hindlimb was conducted by cutting the sciatic and femoral nerves.

Results

In normal rats, significantly increased MBF after MA were observed only in muscles which were penetrated by an acupuncture needle. The size of the increase depended on the number of times of pecking and seemed to be sustained at least until 60 minutes after MA. However, the increase was observed after both acute and chronic denervation. On the other hand, the mean arterial blood pressure (MAP) did not change significantly before, during or after MA.

Conclusion

These results suggest that MA could increase muscle blood flow locally in a dose-dependent manner and that this increase may be caused by local vasodilators, as well as the axon reflex. A further study is needed to elucidate the mechanism.

Effects of acupuncture at the ST-36 point on muscle sympathetic nerve activity and blood pressure in normal adults

The aim of the present study was to determine the effects of acupuncture on post-ganglionic muscle sympathetic nerve activity (MSNA) in humans. MSNA was measured in 8 healthy adult males by microneurography evaluation of the left peroneal nerve. Blood pressure (BP) and heart rate (HR) were simultaneously recorded. MSNA was evaluated as the burst rate, with total MSNA, BP and HR normalized to their respective baseline values. After 10min of rest in the supine position, acupuncture was applied to the right ST-36 point in the tibialis anterior muscle for 15min, with recovery then monitored over a 20-min period. While the burst rate and total MSNA remained constant throughout the study, there was a significant decrease in BP during the real but not sham acupuncture procedure (p<0.05). HR did not significantly change throughout the study. The results rule out the role of MSNA in the BP fall during acupuncture at the ST-36 point, and suggest possible involvement of other factors in the fall of BP.

Mast cell activation in the acupoint is important for the electroacupuncture effect against pituitrin-induced bradycardia in rabbits

This research was conducted to verify the structural and functional characteristics of mast cells in the electroacupuncture (EA) effects on bradycardia. First, we examined the mast cell density at PC 6, adjacent acupoint LU 7, and a non-acupoint. We tested the effects of EA at PC 6 on heart rate (HR) and blood pressure (BP) in rabbits with pituitrin-induced bradycardia. We also injected sodium cromolyn (Cro), a mast cell membrane stabilizer, at PC 6 30 min before EA to investigate if it affected the EA effects. The results showed that in both PC 6 and LU 7, the mast cell densities were higher than in the non-acupoint (P < 0.05). EA could induce mast cell degranulation at PC 6, which could be suppressed by sodium cromolyn (P < 0.05). EA improved HR, though the change was relatively small in the initial stage with a significant change at 35 min after modelling (P < 0.05). BP significantly improved at 10 min after the onset of pituitrin-induced bradycardia (P < 0.05). The EA effects on both HR and BP were suppressed by sodium cromolyn (P < 0.05). Therefore, we concluded that mast cells in the acupoint are important for the EA effects against pituitrin-induced bradycardia in rabbits.

The Effect of Transcutaneous Electrical Nerve Stimulation of Sympathetic Ganglions and Acupuncture Points on Distal Blood Flow

Transcutaneous electrical nerve stimulation (TENS) is a widely-practiced method to increase blood flow in clinical practice. The best location for stimulation to achieve optimal blood flow has not yet been determined. We compared the effect of TENS application at sympathetic ganglions and acupuncture points on blood flow in the foot of healthy individuals. Seventy-five healthy individuals were randomly assigned to three groups. The first group received cutaneous electrical stimulation at the thoracolumbar sympathetic ganglions. The second group received stimulation at acupuncture points. The third group received stimulation in the mid-calf area as a control group. Blood flow was recorded at time zero as baseline and every 3 minutes after baseline during stimulation, with a laser Doppler flow-meter. Individuals who received sympathetic ganglion stimulation showed significantly greater blood flow than those receiving acupuncture point stimulation or those in the control group (p<0.001). Data analysis revealed that blood flow at different times during stimulation increased significantly from time zero in each group. Therefore, the application of low-frequency TENS at the thoracolumbar sympathetic ganglions was more effective in increasing peripheral blood circulation than stimulation at acupuncture points.

Heart Rate Changes in Response to Mechanical Pressure Stimulation of Skeletal Muscles Are Mediated by Cardiac Sympathetic Nerve Activity

Stimulation of mechanoreceptors in skeletal muscles such as contraction and stretch elicits reflexive autonomic nervous system changes which impact cardiovascular control. There are pressure-sensitive mechanoreceptors in skeletal muscles. Mechanical pressure stimulation of skeletal muscles can induce reflex changes in heart rate (HR) and blood pressure, although the neural mechanisms underlying this effect are unclear. We examined the contribution of cardiac autonomic nerves to HR responses induced by mechanical pressure stimulation (30 s, ~10 N/cm²) of calf muscles in isoflurane-anesthetized rats. Animals were artificially ventilated and kept warm using a heating pad and lamp, and respiration and core body temperature were maintained within physiological ranges. Mechanical stimulation was applied using a stimulation probe 6 mm in diameter with a flat surface. Cardiac sympathetic and vagus nerves were blocked to test the contribution of the autonomic nerves. For sympathetic nerve block, bilateral stellate ganglia, and cervical sympathetic nerves were surgically sectioned, and for vagus nerve block, the nerve was bilaterally severed. In addition, mass discharges of cardiac sympathetic efferent nerve were electrophysiologically recorded. Mechanical stimulation increased or decreased HR in autonomic nerve-intact rats (range: −56 to +10 bpm), and the responses were negatively correlated with pre-stimulus HR (r = −0.65, p = 0.001). Stimulation-induced HR responses were markedly attenuated by blocking the cardiac sympathetic nerve (range: −9 to +3 bpm, p < 0.0001) but not the vagus nerve (range: −75 to +30 bpm, p = 0.17). In the experiments with cardiac sympathetic efferent nerve activity recordings, mechanical stimulation increased, or decreased the frequency of sympathetic nerve activity in parallel with HR (r = 0.77, p = 0.0004). Furthermore, the changes in sympathetic nerve activity were negatively correlated with its tonic level (r = −0.62, p = 0.0066). These results suggest that cardiac sympathetic nerve activity regulates HR responses to muscle mechanical pressure stimulation and the direction of HR responses depends on the tonic level of the nerve activity, i.e., bradycardia occurs when the tonic activity is high and tachycardia occurs when the activity is low.

Somatoautonomic reflexes in acupuncture therapy: A review

Oriental therapies such as acupuncture, moxibustion, or Anma, have been used to treat visceral disorders since ancient times. In each of these therapies, stimulation of the skin or underlying muscles leads to excitation of afferent nerves. The sensory information is carried to the central nervous system, where it is transferred to autonomic efferents, thus affecting visceral functions. This neuronal pathway, known as the "somatoautonomic reflex", has been systematically studied by Sato and his colleagues for over a half century. Nearly all their studies were conducted in anesthetized animals, whereas human patients are conscious. Responses in patients or the events following therapeutic somatic stimulation may differ from those observed in anesthetized animals. In fact, it is increasingly apparent that the responses in patients and animals are not always coincident, and the differences have been difficult for clinicians to reconcile. We review the mechanism of the "somatoautonomic reflex" as described in anesthetized animals and then discuss how it can be applied clinically.

Contributions of ADP and ATP to the increase in skeletal muscle blood flow after manual acupuncture stimulation in rats

OBJECTIVE

To investigate the contributions of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) to the increase in skeletal muscle blood flow (MBF) observed following manual acupuncture (MA) stimulation in rats.

METHODS

Male Sprague-Dawley rats were used as experimental animals (300-370 g, n=40). MA was applied to the right tibialis anterior muscle (TA) for 1 min using a stainless steel acupuncture needle. In eight rats, high-performance liquid chromatography with the microdialysis technique was used to measure local extracellular concentrations of ATP, ADP, adenosine monophosphate (AMP), and adenosine in the TA. In the remaining 32 rats, fluorescent microspheres (15 µm in diameter) were used to measure MBF in the TA following pre-treatment with either the P2 receptor antagonist suramin (100 mg/kg intra-arterially) or saline (control) (n=16 each). Rats receiving MA (Suramin+MA and Saline+MA groups, n=8 each) were compared with untreated rats (Suramin and Saline groups, n=8).

RESULTS

MA significantly increased the local extracellular concentration of ATP, ADP, and adenosine (p<0.05, before MA vs 30 min after MA). In addition, MA significantly increased MBF in rats pre-treated with saline or suramin (p<0.01, Saline vs Saline+MA; p<0.05, Suramin vs Suramin+MA, respectively). However, suramin significantly suppressed this MA-induced increase in MBF (p<0.05, Saline+MA vs Suramin+MA).

CONCLUSIONS

These results suggest that both ATP and ADP partially contribute to the MA-induced increase in MBF via P2 receptors. However, further studies are needed to clarify the contributions of other vasodilators.

Electroacupuncture improves cardiac function and remodeling by inhibition of sympathoexcitation in chronic heart failure rats

Chronic heart failure (CHF) is responsible for significant morbidity and mortality worldwide, mainly as a result of neurohumoral activation. Acupuncture has been used to treat a wide range of diseases and conditions. In this study, we investigated the effects of electroacupuncture (EA) on the sympathetic nerve activity, heart function, and remodeling in CHF rats after ligation of the left anterior descending coronary artery. CHF rats were randomly selected to EA and control groups for acute and chronic experiments. In the acute experiment, both the renal sympathetic nerve activity and cardiac sympathetic afferent reflex elicited by epicardial application of capsaicin were recorded. In the chronic experiment, we performed EA for 30 min once a day for 1 wk to test the long-term EA effects on heart function, remodeling, as well as infarct size in CHF rats. The results show EA significantly decreased the renal sympathetic nerve activity effectively, inhibited cardiac sympathetic afferent reflex, and lowered the blood pressure of CHF rats. Treating CHF rats with EA for 1 wk dramatically increased left ventricular ejection fraction and left ventricular fraction shortening, reversed the enlargement of left ventricular end-systolic dimension and left ventricular end-diastolic dimension, and shrunk the infarct size. In this experiment, we demonstrated EA attenuates sympathetic overactivity. Additionally, long-term EA improves cardiac function and remodeling and reduces infarct size in CHF rats. EA is a novel and potentially useful therapy for treating CHF.

Hemodynamic changes in the brachial artery induced by acupuncture stimulation on the lower limbs: a single-blind randomized controlled trial

Acupuncture is commonly performed at acupoints. No comparisons of quantitative physiological alterations in the brachial artery (BA) induced by the stimulation of different acupoints in the lower limbs have been performed in humans. Therefore, we investigated changes in blood flow volume (BFV) in the BA as an indicator of the physiological effects induced by stimulation at 3 points. Seventy-five healthy participants aged 33 ± 9 years (mean ± SD) were enrolled and randomly assigned to 3 groups; they received stimulation at 3 different points located on the lower limbs: ST36, LR3, and a non-acupoint. Stimulation was performed bilaterally with manual rotation of the needles. Using ultrasonography, BFV was measured continuously from rest to 180 seconds after stimulation. LR3 stimulation significantly increased BFV compared to that before needle insertion. Meanwhile, stimulation at ST36 and the non-acupoint significantly decreased BFV compared to that before needle insertion. Stimulation at LR3 elicited a significant increase in BFV compared to that at ST36 and the non-acupoint. The results suggest that the stimulation of different points on the lower limbs causes distinct physiological effects on BFV in the BA.

Acupuncture affects regional blood flow in various organs

In this review, our recent studies using anesthetized animals concerning the neural mechanisms of vasodilative effect of acupuncture-like stimulation in various organs are briefly summarized. Responses of cortical cerebral blood flow and uterine blood flow are characterized as non-segmental and segmental reflexes. Among acupuncture-like stimuli delivered to five different segmental areas of the body; afferent inputs to the brain stem (face) and to the spinal cord at the cervical (forepaw), thoracic (chest or abdomen), lumbar (hindpaw) and sacral (perineum) levels, cortical cerebral blood flow was increased by stimuli to face, forepaw and hindpaw. The afferent pathway of the responses is composed of somatic groups III and IV afferent nerves and whose efferent nerve pathway includes intrinsic cholinergic vasodilators originating in the basal forebrain. Uterine blood flow was increased by cutaneous stimulation of the hindpaw and perineal area, with perineal predominance. The afferent pathway of the response is composed of somatic group II, III and IV afferent nerves and the efferent nerve pathway includes the pelvic parasympathetic cholinergic vasodilator nerves. Furthermore, we briefly summarize vasodilative regulation of skeletal muscle blood flow via a calcitonin gene-related peptide (CGRP) induced by antidromic activation of group IV somatic afferent nerves. These findings in healthy but anesthetized animals may be applicable to understanding the neural mechanisms improving blood flow in various organs following clinical acupuncture.

Effects of Acupuncture on c-Fos Expression in Brain After Noxious Tooth Stimulation of the Rat

Clinically, acupuncture therapy is useful for the control of acute or chronic pain. This study was designed to elucidate the antinociceptive mechanism of acupuncture and the mechanisms underlying cardiovascular reflex elicited by toothache. Expression of c-Fos, a neuronal activation marker, and the phenylethanalamine-N-methyltransferase (PNMT) were examined 1.5 hours after noxious intrapulpal tooth stimulation. Manual acupuncture was performed 20 min before noxious intrapulpal stimulation by 2 M KCl injection into upper or lower anterior tooth pulp. The acupuncture points were Li4 (Hegu) between the 1st and 2nd metacarpal bones or St36 (Zusanli) between the anterior crest of the tibial tuberosity and the fibula head below the patella. After noxious intrapulpal tooth stimulation, Fos-immunoreactive (IR) neurons were identified in the trigeminal subnucleus caudalis (Vc) and the transitional region between the subnucleus caudalis and the subnucleus interpolaris (Vi), in the inferior olivory nucleus (IO) connecting the cerebellum and other brain regions, and also the thalamic ventral posteromedial (VPM) nucleus and centrolateral (CL) nucleus, respectively. In addition, Fos-IR neurons were found in the central cardiovasuclar regulation centers, such as the hypothalamus supraoptic nucleus (SON) and paraventricular nucleus (PVN), and nucleus tractus solitarius (NTS) and rostral ventromedulla (RVLM). All acupuncture at St36 or Li4 significantly suppressed Fos-IR neurons in all Fos-expressed brain areas except the IO nucleus and attenuated the increases in arterial blood pressure (BP) and heart rate (HR) after noxious intrapulpal stimulation. Its Fos-suppressive effects were mostly blocked by naloxone, an opioid antagonist. In addition, acupuncture at St36 or Li4 significantly decreased Fos-containing PNMT, and this effect was also reversed by naloxone. These results suggest that: 1) tooth pulpal noxious signals transmit to the Vc and Vc/Vi transitional region and the 2nd afferent neuron synapse in the thalamic VPM and CL, 2) tooth pulpal pain elicits cardiovascular reflex mediated by NTS, VLM, hypothalamic SON and PVN, and 3) acupuncture reduces cardiovascular reflex elicited by toothache, is associated with the adrenergic system.

Effect of Moxibustion Stimulation of Various Skin Areas on Cortical Cerebral Blood Flow in Anesthetized Rats

The effect of moxibustion stimulation of various skin areas (cheek, forepaw, upper arm, chest, back, lower leg, hindpaw and perineum) on cerebral blood flow (CBF) of the parietal cortex was examined in anesthetized rats after eliminating emotional influences. Moxibustion stimulation was performed by burning a moxa cone of about 4 mg weight placed on the shaved skin. CBF of the parietal cortex was measured using a laser Doppler flowmeter. Stimulation of the cheek, forepaw, upper arm and hindpaw produced significant increases in CBF, but stimulation of the other areas did not produce significant responses. Moxibustion stimulation of the forepaw and hindpaw produced an increase in the mean arterial pressure (MAP), while stimulation of the other areas did not. After spinal transection at the 2nd thoracic level, the MAP response to stimulation of the forepaw was abolished, whereas the CBF response to stimulation of the forepaw remained. The CBF response in spinalized rats was not affected by cutting cervical sympathetic and facial parasympathetic nerves, while it was almost abolished by intravenous administration of muscarinic and nicotinic cholinergic blocking agents. The CBF response was abolished by crushing the brachial plexus ipsilateral to the stimulated side. It is suggested that the increase in CBF, independent of MAP and emotional responses, elicited by moxibustion stimulation is a reflex response whose afferent pathway is composed of somatic afferent nerves, and whose efferent pathway involves intracerebral cholinergic nerves. A contribution of endogenous opioids in the present CBF responses was neglected, because naloxone did not influence the CBF responses.

Neural acupuncture unit: a new concept for interpreting effects and mechanisms of acupuncture

When an acupuncture needle is inserted into a designated point on the body and mechanical or electrical stimulation is delivered, various neural and neuroactive components are activated. The collection of the activated neural and neuroactive components distributed in the skin, muscle, and connective tissues surrounding the inserted needle is defined as a neural acupuncture unit (NAU). The traditionally defined acupoints represent an anatomical landmark system that indicates local sites where NAUs may contain relatively dense and concentrated neural and neuroactive components, upon which acupuncture stimulation would elicit a more efficient therapeutic response. The NAU-based local mechanisms of biochemical and biophysical reactions play an important role in acupuncture-induced analgesia. Different properties of NAUs are associated with different components of needling sensation. There exist several central pathways to convey NAU-induced acupuncture signals, Electroacupuncture (EA) frequency-specific neurochemical effects are related to different peripheral and central pathways transmitting afferent signals from different frequency of NAU stimulation. More widespread and intense neuroimaging responses of brain regions to acupuncture may be a consequence of more efficient NAU stimulation modes. The introduction of the conception of NAU provides a new theoretical approach to interpreting effects and mechanisms of acupuncture in modern biomedical knowledge framework.

Electrical stimulation of deep peroneal nerve mimicking acupuncture inhibits the pressor response via capsaicin-insensitive afferents in anesthetized rats

OBJECTIVE

To assess the inhibitory modulation of blood pressure by stimulation of the deep peroneal nerve (DPN) and to determine the involvement of nociceptive fibers in the modulation.

METHODS

All the animals were divided into six groups (A-F). The rats in groups A and B received no pretreatment. The rats in groups C and D received subcutaneous injection of capsaicin or control vehicle, respectively, near the DPN for 2 days. Those in groups E and F had the DPN exposed to capsaicin or control vehicle, respectively, for 20 min. Subsequently, pressor responses were induced by stimulation of paraventricular nucleus (PVN) either electrically (groups A and C C-F) or chemically via injection of glutamate (group B). After two stable pressor responses (baseline), all groups were subject to 5-min DPN stimulation followed by PVN stimulation for 10 s. Arterial blood pressure, heart rate, and electrocardiogram were recorded. The pressor response was calculated as the difference in the mean arterial pressure (MAP) before and after PVN stimulation, and changes from baseline in pressor response after DPN stimulation were compared between the groups.

RESULTS

Increases of MAP of 22.88±2.18 mm Hg and 20.32±5.25 mm Hg were induced by electrical (group A) or chemical (group B) stimulation of the PVN, respectively. These pressor responses were inhibited by stimulation of the DPN, and the MAP was reduced to 12.00±2.10 mm Hg in group A (n=6, P<0.01) and 7.00±2.85 mm Hg in group B (n=6, P<0.01). Subcutaneous injection of capsaicin (125 mg/kg) near the DPN in group C (n=7) had no effect on the inhibitory effect of DPN stimulation compared with the group D (n=9), and neither did blockade of nociceptive fibers with capsaicin in group E (n=6) compared with group F (n=8).

CONCLUSION

Stimulation of the DPN mimicking acupuncture has an inhibitory effect on the pressor response, and the effect is mediated by capsaicin-insensitive afferent fibers in the DPN.

Regulation of the cardiovascular function by CO2 laser stimulation in anesthetized rats

Physical stimulation of body surface points is known to affect various organ functions. In traditional Chinese medicine, so-called acupoints were defined. These points can be physically stimulated to effectively treat various diseases. Here we describe for the first time the effect of CO(2) laser stimulation at the acupoints Neiguan (PC-6), Quchi (LI-11), Zusanli (ST-36), and Taichong (LR-3) on heart rate and mean arterial blood pressure in anesthetized rats. CO(2) laser stimulation increased the skin surface temperature to 54°C. Our results revealed that the laser stimulation at the left or right PC-6 and LR-3 increased heart rate and mean arterial pressure. There was no response of heart rate and mean arterial pressure during and after stimulation of the left LI-11, but laser stimulation at the right LI-11 slightly increased heart rate and mean arterial pressure. On the other hand, laser stimulation at the left and right ST-36 decreased heart rate and mean arterial pressure. The effects on mean arterial pressure were more pronounced than those on heart rate. After full spinal cord transection, all heart-rate and mean-arterial-pressure responses were attenuated or completely abolished. These results suggest that CO(2) laser stimulation at either the left or right PC-6, ST-36, and LR-3, as well as at the right LI-11 can modulate the cardiovascular functions in anesthetized rats, and its modulatory site might be supraspinal.

Assessing the effects of acupuncture by comparing needling the hegu acupoint and needling nearby nonacupoints by spectral analysis of microcirculatory laser Doppler signals

We aimed to assess the effects of acupuncture by analyzing the frequency content of skin blood-flow signals simultaneously recorded at the Hegu acupoint and two nearby nonacupoints following acupuncture stimulation (AS). Laser Doppler flowmetry (LDF) signals were measured in male healthy volunteers in two groups of experiments: needling the Hegu acupoint (n = 13) and needling a nearby nonacupoint (control experiment; n = 10). Each experiment involved recording a 20 min baseline-data sequence and two sets of effects data recorded 0–20 and 50–70 min after stopping AS. Wavelet transform with Morlet mother wavelet was applied to the measured LDF signals. Needling the Hegu acupoint significantly increased the blood flow, significantly decreased the relative energy contribution at 0.02–0.06 Hz and significantly increased the relative energy contribution at 0.4–1.6 Hz at Hegu, but induced no significant changes at the nonacupoints. Also, needling a nearby nonacupoint had no effect in any band at any site. This is the first time that spectral analysis has been used to investigate the microcirculatory blood-flow responses induced by AS, and has revealed possible differences in sympathetic nerve activities between needling the Hegu acupoint and its nearby nonacupoint. One possible weakness of the present design is that different De-Qi feelings following AS could lead to nonblind experimental setup, which may bias the comparison between needling Hegu and its nearby nonacupoint. Our results suggest that the described noninvasive method can be used to evaluate sympathetic control of peripheral vascular activity, which might be useful for studying the therapeutic effects of AS.

Acupuncture-like stimulation at auricular point Heart evokes cardiovascular inhibition via activating the cardiac-related neurons in the nucleus tractus solitarius

Fifty-eight male Sprague-Dawley rats used in the present study to investigate the role of baroreceptor sensitive neurons of the nucleus tractus solitarius (NTS) in the regulation of cardiovascular inhibition during acupuncture at the auricular point Heart, single unit recording was made in anesthetized Sprague-Dawley rats. A neuron was considered to be excited or inhibited by acupuncture stimulation if it displayed 15% more or less spikes s(-1), respectively. NTS neurons were classified into cardiac-related (CR) neurons and non-cardiac-related neurons based on whether their rhythmic discharges were synchronized with the R-waves and responding to sodium nitroprusside (NP; 20 μg/kg, i.v.) administration. Manual acupuncture was applied at the auricular point Heart and somatic acupuncture points ST36 and PC6. Acupuncture at auricular point Heart showed a more significant inhibitory effect on arterial pressure (-22.1±2.4mm Hg; P<0.001) and heart rate (-12.7±1.7 bpm; P<0.001) than that at ST36 and PC6. Acupuncture at auricular point Heart also increased the level of response of CR neurons in the NTS (93.8%±26.0% increase in discharge rate; P<0.01). Systemic or local administration of atropine attenuated the cardiovascular inhibition and activation of CR neurons evoked by auricular acupuncture, but had no effect on the same responses evoked by somatic acupuncture. Inactivation of the NTS with local anesthetics also decreased the cardiovascular inhibitory responses evoked by auricular acupuncture. Our results show that acupuncture at the auricular point Heart regulates cardiovascular function by activating baroreceptor sensitive neurons in the NTS in a similar manner as the baroreceptor reflex in cardiovascular inhibition.

Peripheral muscarinic receptors mediate the anti-inflammatory effects of auricular acupuncture

BACKGROUND

The cholinergic and opioid systems play important roles in modulating inflammation. This study tests whether auricular acupuncture (AA) produces anti-inflammatory effects via opioid and peripheral cholinergic receptors in a rat model.

METHODS

Rats were anesthetized with chloral hydrate and inflammation was induced by intraplantar injection of carrageenan. Electroacupuncture was performed at auricular points bilaterally. The severity of inflammation was assessed using changes in paw volume and thermal and mechanical pain thresholds of the rats during recovery from anesthesia.

RESULTS

Electroacupuncture at selected auricular acupoints significantly reduced paw edema and mechanical hyperalgesia, with no significant effect on thermal hyperalgesia. The anti-edematous and analgesic effects of AA were abolished by blockade of peripheral cholinergic muscarinic receptors with methyl atropine. Blockade of local muscarinic receptors at the inflamed site with a small dose of atropine also antagonized the anti-edematous effect of AA. By contrast, systemic opioid receptor blockade with naloxone did not antagonize the anti-inflammatory effects of AA.

CONCLUSION

This study discovers a role of peripheral muscarinic receptors in mediating the anti-inflammatory effects of AA. The cholinergic muscarinic mechanism appears to be more important than the opioid mechanism in the anti-inflammatory action of AA.

Afferent nerve fibers and acupuncture

Acupuncture has been used for analgesia, for treating visceral function disorders and for improving motor functions. It is well established that stimulation of the skin and muscles, either electrically or with noxious or non-noxious stimuli, induces a variety of somato-motor and autonomic responses. This strongly suggests that acupuncture acts by exciting cutaneous and/or muscular afferent nerve fibers. A question of considerable scientific and practical interest is what kinds of somatic afferent fibers are stimulated by acupuncture and are involved in its effects. There are several types of afferent fiber: thick myelinated Aα and Aβ (group I and II), thin myelinated Aδ (group III) and thinner unmyelinated C (group IV) fibers. In recent studies we have tried to establish which ones of these types of somatic afferent fiber are stimulated by acupuncture. In this article we first review the experimental evidence showing that the effects of acupuncture are mediated by the activation of afferent nerve fibers innervating the skin and muscles. Secondly, we discuss what types of afferent nerve fiber are activated by electrical acupuncture, and what types are involved in its effects on somato-motor functions and on visceral functions. Finally, we present some new findings based on recordings from single afferent nerve fibers excited by manual acupuncture.

Neural mechanisms of reflex inhibition of heart rate elicited by acupuncture-like stimulation in anesthetized rats

We briefly review our recent studies on the neural mechanisms of the reflex effects of acupuncture-like stimulation on heart rate in rats. In pentobarbital anesthetized rats, acupuncture-like stimulation of one of various segmental areas of the body (forelimb, chest, abdomen, hindlimb) invariably induces a decrease in heart rate. In the case of the hindlimb, the effect can be produced by stimulation of the muscles alone but not of skin alone, and is abolished by severance of the hindlimb somatic nerves. Electrical stimulation of groups III and IV nerve fibers (in the tibial nerve) decreases heart rate. Decrease in heart rate by acupuncture-like stimulation of a hindlimb is accompanied by a decrease in cardiac sympathetic nerve activity, and is abolished by cardiac sympathectomy but not by vagotomy. High spinal cord transection or infusion of the GABA(A) receptors antagonist, bicuculline, into the cisterna magna is effective in disrupting the reflex bradycardia. Opioid receptor blockade does not disrupt the reflex arc. We conclude that the reflex pathway involved in the decrease of heart rate by acupuncture-like stimulation comprises groups III and IV muscle afferent nerves whose activation stimulates GABAergic neurons in the brainstem and inhibits sympathetic outflow to the heart. When the sympathetic tone is high due to hypercapnia, the induced reduction in both cardiac sympathetic nerve activity and heart rate is not augmented, suggesting that the magnitude of sympatho-inhibitory response to acupuncture-like stimulation does not depend on pre-existing sympathetic tone.

Sympatho-inhibitory response of the heart as a result of short-term acupuncture-like stimulation of the rat hindlimb is not augmented when sympathetic tone is high as a result of hypercapnia

This study examined whether the sympatho-inhibitory response of the heart to acupuncture-like stimulation of a hindlimb in anesthetized rats depends on the sympathetic tone. Observed reductions in both cardiac sympathetic nerve activity and heart rate following short-term acupuncture-like stimulation of a hindlimb were not augmented when the sympathetic tone was high as a result of hypercapnia.

Effects of acupuncture at the Hoku acupoint on the pulsatile laser Doppler signal at the heartbeat frequency

We aimed to assess the effects of acupuncture by analyzing the alternating current (AC) component of skin blood-flow signals (around the heartbeat frequency) simultaneously recorded at the Hoku acupoint, which is an important acupoint in oriental medicine, and two nearby non-acupoints following acupuncture stimulation (AS). Laser Doppler flowmetry signals were measured in 28 experiments on nine volunteers. Each experiment involved the recording of a 20-min control-data sequence and two sets of effects data recorded 0-20 min and 50-70 min after the AS had been stopped. The direct current (DC) and AC components (DCflux and ACflux, respectively), pulse width (PW), and foot delay time (FDT) of the flux signal were calculated. The DCflux, ACflux, PW, and FDT were all significantly increased only at Hoku following AS. Regression analysis between the DCflux and ACflux revealed that the slope was largest (>1) at Hoku among the measurement sites. Our results indicated that both the DCflux and ACflux in the microcirculatory perfusion were increased by stimulation at the Hoku acupoint, with the change being greatest for the latter. Parameters calculated from the pulsatile flux waveform, such as the PW and FDT, could contribute to noninvasive evaluations of the sympathetic neural activities and of the improvement in perfusion following AS.

Mechanism of the reflex inhibition of heart rate elicited by acupuncture-like stimulation in anesthetized rats

Acupuncture or acupuncture-like stimulation applied to different body areas can modify autonomic nerve activity to various organs, including gut, bladder, adrenal medulla, and the heart. We studied the reflex bradycardia in response to insertion into the skin and underlying muscles and twisting of an acupuncture needle in pentobarbital-anesthetized rats. We found that acupuncture-like stimulation of forelimb, hindlimb, chest, and abdomen all produced significant heart rate decreases. Rate minima were reached at the end of the 60-second stimulation episode and significant bradycardia persisted for about 40 s after stimulation ended. Heart rate decreases were paralleled by decreases in cardiac sympathetic nerve activity, and could be produced by electrical stimulation of group IV muscle afferent fibers (tibial nerve). Electrical stimulation of the tibial nerve at rates as low as 0.1-2 Hz was effective for eliciting heart rate decreases. Nerve fiber groups were defined by stimulation of and recording from tibial nerve. Activation of groups I, II, or III fiber was ineffective for eliciting the reflex bradycardia. Sympathectomy, high spinal transection, or infusion of the GABA(A) receptor antagonist, bicuculline, into the cisterna magna were all effective for disrupting the reflex bradycardia. Vagotomy and opioid receptor blockade were ineffective for disrupting the reflex pathway. We conclude that the reflex pathway to decrease heart rate by acupuncture-like stimulation consists of mainly group IV muscle afferent fibers whose activity (even very low rate of activity) leads to the activation of GABA-ergic neurons in the brainstem and an inhibition of sympathetic outflow to the heart.

Investigation of specificity of auricular acupuncture points in regulation of autonomic function in anesthetized rats

Auricular acupuncture has been used for various autonomic disorders in clinical practice. It has been theorized that different auricular areas have distinct influence on autonomic functions. The present study aims to examine the effects of acupuncture stimulation at different auricular areas on cardiovascular and gastric responses. In male Sprague-Dawley rats anesthetized with pentobarbital sodium, five auricular areas, which were located at the apex of the helix (A(1)), the middle of the helix (A(2)), the tail of the helix (A(3)), the inferior concha (A(4)) and the middle of the antihelix (A(5)), had been selected for stimulation with manual acupuncture (MA) and different parameters of electroacupuncture (EA). A mild depressor response (6%-12% decrease from baseline) was evoked from A(1), A(3) and A(4) by MA and from all five areas by EA (100 Hz-1 mA). The biggest depressor response (-18.4+/-3.1 mmHg, p<0.001) was evoked from A(4). A small bradycardia was evoked by MA from A(4) and by EA at A(3), A(4) and A(5.) Increase in intragastric pressure (8-14 mmH(2)O) was evoked by MA from A(1), A(3) and A(4) and by EA at A(2.) These results show that similar patterns of cardiovascular and gastric responses could be evoked by stimulation of different areas of the auricle. The present results do not support the theory of a highly specific functional map in the ear. Rather, there is a similar pattern of autonomic changes in response to auricular acupuncture, with variable intensity depending on the area of stimulation.

Neural mechanism of bradycardiac responses elicited by acupuncture-like stimulation to a hind limb in anesthetized rats

The effects of acupuncture-like stimulation of a hind limb on heart rate were examined in anesthetized rats. An acupuncture needle, having a diameter of either 160 or 340 microm, was inserted into the skin and underlying muscles at a depth of about 5 mm and twisted right and left twice every second for 1 min. Stimulation by a needle with a diameter of either 160 or 340 microm produced a decrease in heart rate. Severance of the femoral and sciatic nerves ipsilateral to the hind-limb stimulation completely abolished the bradycardiac response. Also, heart rate was significantly decreased by acupuncture-like stimulation of the hind-limb muscles alone, but was not significantly influenced by the stimulation of the hind-limb skin alone. The bradycardiac response induced by acupuncture-like stimulation was not influenced by bilateral severance of the vagal nerves at the cervical level, but was abolished by bilateral stellectomy. Acupuncture-like stimulation of the hind limb induced a decrease in the activity of the cardiac sympathetic efferent nerve as well as a decrease in heart rate. These results indicate that the decrease in heart rate induced by acupuncture-like stimulation of a hind limb is a reflex response. The afferent pathway is composed of hind-limb muscle afferents, and the efferent pathway is composed of cardiac sympathetic nerves.

The alpha-adrenoceptor mediation of the immunomodulatory effects of electroacupuncture in DNP-KLH immunized mice

Our previous study demonstrated that successive electroacupuncture (EA) at ST36 acupoint reduces IgE production in BALB/c mice immunized with 2,4-dinitrophenylated keyhole limpet protein (DNP-KLH) by suppression of the Th2 cell lineage development. Here, we report that pretreatment of phentolamine (alpha-adrenoceptor antagonist, 10mg/kg, i.p.) completely blocks the EA-induced suppression of antigen-specific and total IgE levels in serum and IL-4 production in anti-CD3 mAb-activated splenocytes in DNP-KLH immunized mice. The results suggest that alpha-adrenoceptor play an important role in mediating the suppressive effects of EA on IgE production and Th2 cell response in DNP-KLH immunized mice.

Acupuncture on the blood flow of various organs measured simultaneously by colored microspheres in rats

We examined how acupuncture affected the blood flow of muscle, kidney, stomach, small intestine, brain, lung, heart, spleen and liver. Wistar rats anesthetized with urethane (n = 27) were allocated into the control (n = 10), ST-7 (Hsia-Kuan, n = 10) and LI-4 (Hoku, n = 7) groups. To measure organ blood flow, colored microspheres (CMS) were injected through a catheter positioned in the left ventricle and blood samples were drawn from the femoral artery. Yellow CMS (3.6–4.2 × 10⁵) and blue CMS (6.0–6.9 × 10⁵) were injected at intervals of about 30 min. An acupuncture needle (φ 340 μm) was inserted into the left ST-7 point (left masseter muscle) or the right LI-4 point after the first sampling and left for about 30 min (10 twists at 1 Hz, 2-min intervals). The mean blood flow of nine organs varied widely from 4.03 to 0.20 (ml/min/g). Acupuncture to the ST-7 produced significant changes of the blood flow (percentage change from baseline) in the muscle, kidney, brain and heart (P < 0.05, versus control), but those of LI-4 were not significant. The blood flow of the left masseter muscle after acupuncture to ST-7 (left masseter muscle) tended to increase (P = 0.08). Changes in blood pressure during the experimental periods were almost similar among these three groups. Acupuncture stimulation increases the blood flow of several organs by modulating the central circulatory systems, and the effects differed with sites of stimulation.

Specific acupuncture sensation correlates with EEGs and autonomic changes in human subjects

Sympathetic overactivation is suggested to be associated with chronic pain syndrome, and acupuncture is frequently applied in therapy for this syndrome. Furthermore, the forebrain including the various cerebral cortices has been implicated in inhibitory and facilitatory control of pain as well as autonomic functions. We investigated relationships among specific sensations induced by acupuncture manipulation, effects on sympathetic and parasympathetic autonomic functions, and EEG changes. An acupuncture needle was inserted into the right trapezius muscle of the subjects, and acupuncture manipulation was repeated to induce specific acupuncture sensation repeatedly while the needle was left in the muscle. Acupuncture manipulation significantly decreased heart rate (HR), and increased systolic blood pressure (SBP). Spectral analysis indicated that acupuncture manipulation significantly decreased low frequency components (LF) of both HR variability (HRV) and SBP variability (SBPV), and significantly reduced ratio of LF to high frequency component (HF) of HRV (LF/HF, index of sympathetic activity). Furthermore, there was a significant negative correlation between changes in LF/HF ratio of HRV and the number of specific acupuncture sensations reported, and a significant positive correlation between HF of HRV and the number of acupuncture sensations. Analyses of EEG data indicated that acupuncture manipulation non-specifically increased power of all spectral bands except the gamma band. Furthermore, changes in HF (index of parasympathetic activity) and total power (overall activity of the autonomic nervous system) of HRV were positively correlated with changes in theta, alpha, and gamma power, while changes in LF of SBPV and LF/HF of HRV were negatively correlated with changes in power of all spectral bands. These results are consistent with the suggestion that autonomic changes induced by manipulation inducing specific acupuncture sensations might be mediated through the central nervous system, especially through the forebrain as shown in EEG changes, and are beneficial to relieve chronic pain by inhibiting sympathetic nervous activity.

Short-term electroacupuncture at Zusanli resets the arterial baroreflex neural arc toward lower sympathetic nerve activity

Although electroacupuncture reduces sympathetic nerve activity (SNA) and arterial pressure (AP), the effects of electroacupuncture on the arterial baroreflex remain to be systematically analyzed. We investigated the effects of electroacupuncture of Zusanli on the arterial baroreflex using an equilibrium diagram comprised of neural and peripheral arcs. In anesthetized, vagotomized, and aortic-denervated rabbits, we isolated carotid sinuses and changed intra-carotid sinus pressure (CSP) from 40 to 160 mmHg in increments of 20 mmHg/min while recording cardiac SNA and AP. Electroacupuncture of Zusanli was applied with a pulse duration of 5 ms and a frequency of 1 Hz. An electric current 10 times the minimal threshold current required for visible muscle twitches was used and was determined to be 4.8 +/- 0.3 mA. Electroacupuncture for 8 min decreased SNA and AP (n = 6). It shifted the neural arc (i.e., CSP-SNA relationship) to lower SNA but did not affect the peripheral arc (i.e., SNA-AP relationship) (n = 8). SNA and AP at the closed-loop operating point, determined by the intersection of the neural and peripheral arcs, decreased from 100 +/- 4 to 80 +/- 9 arbitrary units and from 108 +/- 9 to 99 +/- 8 mmHg (each P < 0.005), respectively. Peroneal denervation eliminated the shift of neural arc by electroacupuncture (n = 6). Decreasing the pulse duration to <2.5 ms eliminated the effects of SNA and AP reduction. In conclusion, short-term electroacupuncture resets the neural arc to lower SNA, which moves the operating point toward lower AP and SNA under baroreflex closed-loop conditions.

Responses of Blood Pressure and Renal Sympathetic Nerve Activity to Colorectal Distension in Anesthetized Rats

We investigated the effects of visceral stimulation by colorectal distension (CRD) on mean arterial blood pressure (MAP) and renal sympathetic nerve activity (RSNA), the latter being an index of vasoconstrictor activity, in anesthetized central nervous system (CNS)-intact and C2 spinalized rats. The CRD stimulation was induced by the distention of a balloon inserted into the colorectum. In CNS-intact rats, there were significant reductions in MAP and RSNA in response to intraballoon pressures of 60 and 80 mmHg, but not to 20 and 40 mmHg. However, spinalized rats demonstrated significant increases in MAP in response to intraballoon pressures of 60 and 80 mmHg and increases in RSNA in response to intraballoon pressures of 40, 60, and 80 mmHg. These results suggest that noxious visceral stimulation at lower spinal levels reduces MAP by inhibiting sympathetic output in CNS-intact anesthetized rats. On the other hand, noxious visceral stimulation results in an increase in sympathetic-induced MAP in spinalized anesthetized rats.

Manual acupuncture needle stimulation of the rat hindlimb activates groups I, II, III and IV single afferent nerve fibers in the dorsal spinal roots

Using single unit nerve recording techniques in rats, the present experiment aimed to determine which specific population of afferent nerve fibers (groups I, II, III and IV) in the dorsal roots at the 4th or 5th lumbar segments (L4 or L5) are activated during manual acupuncture needle stimulation. An acupuncture needle 300-340 microm in diameter was inserted into the skin and underlying muscles around the Zusanli acupoint (ST36) area in the hindlimbs, and was manually rotated right and left at a frequency of about 1 Hz for 1 min. The dorsal root of the L4 and L5 spinal nerve was cut close to the entrance into the spinal cord after laminectomy and dissected free to record unitary afferent nerve activity. A single afferent fiber activated by acupuncture stimulation was identified by the identical shape of the discharge spikes during stimulation and during electrically evoked action potentials induced by single pulse electrical stimulation of the sciatic nerve. The conduction velocity of the afferent fiber was calculated by the latency of the electrically evoked action potential. A total of 35 units were intentionally recorded from all animals in order to include all 4 afferent fiber groups. Units were spontaneously silent in the absence of stimulation, while all units responded to ipsilateral manual rotation of the acupuncture needle. The conduction velocity of all 35 units ranged between 0.8 and 86.0 m/s, thus belonging to groups I-V fibers. Mean conduction velocity of groups I, II, III and IV were 57.9 m/s (n = 13), 42.9 m/s (n = 11), 10.3 m/s (n = 6) and 1.2 m/s (n = 5), respectively. Mean discharge rates during acupuncture stimulation of groups I, II, III and IV afferents were 7.4 Hz, 6.2 Hz, 4.7 Hz and 0.4 Hz, respectively. Discharge rates of group IV afferent fibers were significantly lower than those of groups I, II and III afferents. It was concluded that manual acupuncture needle stimulation to the hindlimbs activated afferent nerve fibers belonging to all four groups of afferents in rats. It is suggested that all four groups of somatic afferents activated by manual acupuncture stimulation will elicit various effects when action potentials are delivered to the central nervous system.

Evaluation of electroacupuncture treatment of horses with signs of chronic thoracolumbar pain

OBJECTIVE

To evaluate use of electroacupuncture for treatment of horses with signs of chronic thoracolumbar pain.

DESIGN

Prospective study.

ANIMALS

15 horses with signs of chronic thoracolumbar pain.

PROCEDURE

Horses were randomly allocated to 1 of 3 treatment groups. Horses in group 1 received electroacupuncture stimulation (once every 3 days for 5 treatments), those in group 2 received phenylbutazone (2.2 mg/kg [1 mg/lb], PO, q 12 h, for 5 days), and those in group 3 received saline (0.9% NaCl) solution (20 mL, PO, q 12 h, for 5 days). Thoracolumbar pain scores (TPSs) were evaluated before (baseline) and after each treatment.

RESULTS

Mean +/- SE TPSs in horses receiving phenylbutazone or saline solution did not change significantly during the study. After the third treatment, mean +/- SE TPS (2.1 +/- 0.6) in horses receiving electroacupuncture stimulation was significantly lower than baseline (6.0 +/- 0.6) TPS. Mean +/- SE TPSs in horses receiving electroacupuncture stimulation were significantly lower than baseline TPSs and TPSs in horses receiving phenylbutazone or saline solution after the third treatment to 14 days after the last treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

TPSs are useful for evaluating the efficacy of various analgesic methods used for treatment of thoracolumbar pain in horses. Electroacupuncture was effective for treatment of chronic thoracolumbar pain in horses. Results provided evidence that 3 sessions of electroacupuncture treatment can successfully alleviate signs of thoracolumbar pain in horses. The analgesic effect induced by electroacupuncture can last at least 2 weeks. Phenylbutazone administered PO did not effectively alleviate signs of thoracolumbar pain in horses in this study.