Electroacupuncture enhances preproenkephalin mRNA expression in rostral ventrolateral medulla of rats

The Hypotensive Role of Acupuncture in Hypertension: Clinical Study and Mechanistic Study

As a component of traditional Chinese medicine (TCM), acupuncture has the potential to lower blood pressure (BP) in patients with hypertension. Emerging evidence indicates that the acupuncture-induced inhibition of high BP occurs through the activation of the pathway in the afferent, central, and efferent pathways. An increasing number of studies have demonstrated that acupuncture not only activates distinct brain regions under conditions of hypertension caused by an imbalance between the sympathetic and parasympathetic systems but also modulates neurotransmitters in related brain regions to alleviate the autonomic response. The activity of these pathways can be assessed by injecting agonists or inhibitors or by performing neurotomy. This review focuses on the clinical and mechanistic studies of acupuncture in modulating BP, which might provide a neurobiological foundation for the effects of acupuncture. Although many mechanisms underlying the effects of acupuncture on cardiovascular function have been identified, further investigation is warranted.

Adenosine Receptor A2a, but Not A1 in the rVLM Participates Along With Opioids in Acupuncture-Mediated Inhibition of Excitatory Cardiovascular Reflexes

Electroacupuncture (EA) can be used to lower high blood pressure (BP) in clinical practice. However, precise mechanisms underlying its effects on elevated BP remain unclear. Our previous studies have shown that EA at the P5-6 acupoints, overlying the median nerve, attenuates elevated BP induced by gastric distension (GD) through influence on rostral ventrolateral medulla (rVLM). Although adenosine is released during neuronal activation in the rVLM, its role in acupuncture-cardiovascular regulation is unknown. The purinergic system is involved in cardiovascular pressor and depressor responses, including via selective activation of A₁ and A_{2 a} rVLM receptors, respectively. The action of A_{2 a} receptor stimulation in the central nervous system may be further regulated through an endogenous opioid mechanism. However, it is uncertain whether this putative action occurs in the rVLM. We hypothesized that adenosine in the rVLM contributes to EA modulation of sympathoexcitatory reflexes through an A_{2 a} but not an A₁ adenosine receptor-opioid mechanism. EA or sham-EA was applied at the P5-6 acupoints in Sprague-Dawley male rats subjected to repeated GD under anesthesia. We found that EA (n = 6) but not sham-EA (n = 5) at P5-6 significantly (P < 0.05) attenuated GD-induced elevations in BP. EA modulation of sympathoexcitatory cardiovascular reflexes was reversed significantly after rVLM microinjection (50 nl) of 8-SPT (10 mM; non-selective adenosine receptor antagonist; n = 7) or SCH 58261 (1 mM; A_{2 a} receptor antagonist; n = 8; both P < 0.05), but not by DPCPX (3 mM; A₁ receptor antagonist; n = 6) or the vehicle (5% dimethylsulfoxide; n = 6). Moreover, microinjection of an A_{2 a} receptor agonist, CGS-21680 (0.4 mM; n = 8) into the rVLM attenuated GD-induced pressor responses without EA, which mimicked EA's inhibitory effects (P < 0.05). After blockade of opioid receptors with naloxone (1 mM) in the rVLM, SCH 58261's reversal of EA's effect on GD-induced pressor responses was blunted, and CGS-21680-mediated inhibitory effect on pressor responses was not observed. Furthermore, neurons labeled with adenosine A_{2 a} receptors were anatomically co-localized with neurons stained with enkephalin in the rVLM. These data suggest that the involvement of rVLM adenosine A_{2 a} receptors in EA modulation of GD-induced pressor reflexes is, at least in part, dependent on the presence of endogenous opioids.

Changes in cerebral glucose metabolism after acupuncture at KI3 in spontaneously hypertensive rats: a positron emission tomography study

Objective:

The aim of this study was to explore the effect of acupuncture stimulation at KI3 on brain glucose metabolism in spontaneously hypertensive rats (SHRs).

Methods:

Brain glucose metabolism in SHRs after acupuncture stimulation at KI3 was detected using 18F-2-fluorodeoxy-D-glucose positron emission tomography (18F-FDG-PET). SHRs were randomly divided into three groups: no treatment (SHR group); acupuncture at KI3 (KI3 group); and sham acupuncture (Sham group). Wistar Kyoto (WKY) rats were used as a normal blood pressure (BP) control group. Rats were subjected to 10 min of acupuncture once a day for 7 days. BP and positron emission tomography–computed tomography (PET-CT) were measured after the first acupuncture session and after 7 days of treatment.

Results:

The results showed that BP was lower in the KI3 group than in the SHR group, both 30–60 min after the first acupuncture session and 24–48 h after the 7-day treatment. Compared with the WKY group, the SHR group had lower glucose metabolism in the motor cortex, sensory cortex, basal ganglia, corpus callosum, caudate putamen, and visual cortex. Compared with the untreated/sham-treated SHR control groups, cerebral glucose metabolism was lower in the medulla oblongata, thalamus, dorsal thalamus, orbital cortex, and hypothalamus after acupuncture at KI3, while it was higher in the olfactory cortex and inferior phrenic muscle.

Conclusion:

Our results show that, in SHRs, needling at KI3 reduces high BP, most likely by altering the activation of cerebral regions.

Remifentanil Requirement for Inhibiting Responses to Tracheal Intubation and Skin Incision Is Reduced in Patients With Parkinson's Disease Undergoing Deep Brain Stimulator Implantation

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease affecting the quality of life in the elderly. We speculated that PD patients might have abnormal pharmacodynamics due to the degenerative neural system, and the present study was performed to investigate the pharmacodynamics of remifentanil in PD patients.

MATERIALS AND METHODS

Two arms of patients were recruited, including 31 PD patients undergoing pulse generator placement after deep brain stimulator implantation and 31 pair-controlled patients undergoing intracranial surgery without PD (NPD). Patients were anesthetized with target-controlled infusion of propofol and remifentanil. The effective concentration of remifentanil to inhibit responses to intubation and skin incision in 50% and 95% patients (EC50 and EC95) was determined by the up and down method.

RESULTS

Demographic data, bispectral index, and hemodynamic values were similar between the PD and the NPD groups. The average remifentanil concentration used in the PD group for tracheal intubation is significantly lower than in the NPD group (P<0.001). The EC50 for inhibiting the response to tracheal intubation were 1.86 ng/mL (95% confidential interval [CI], 1.77-1.96 ng/mL) in the PD group and 3.20 ng/mL (95% CI, 3.13-3.27 ng/mL) in the NPD group. The average remifentanil concentration used in the PD group for skin incision is significantly lower than in the NPD group (P<0.001). EC50 for inhibiting the response to skin incision were 2.17 ng/mL (95% CI, 2.09-2.25 ng/mL) in the PD group and 3.09 ng/mL (95% CI, 3.02-3.17 ng/mL) in the NPD group.

CONCLUSIONS

The remifentanil concentrations required for inhibiting responses to tracheal intubation and skin incision are reduced markedly in PD patients undergoing pulse generator placement (NCT01992692).

Mechanical Stimulation of the HT7 Acupuncture Point to Reduce Ethanol Self-Administration in Rats

Background

Alcoholism, which is a disabling addiction disorder, is a major public health problem worldwide. The present study was designed to determine whether the application of acupuncture at the Shenmen (HT7) point suppresses voluntary alcohol consumption in addicted rats and whether this suppressive effect is potentiated by the administration of naltrexone.

Methods

Rats were initially trained to self-administer a sucrose solution by operating a lever. A mechanical acupuncture instrument (MAI) for objective mechanical stimulation was used on rats whose baseline response had been determined. In addition, the effect of HT7 acupuncture on beta-endorphin concentration and ethanol intake via naltrexone were investigated in different groups.

Results

We found that ethanol intake and beta-endorphin level in rats being treated with the MAI at the HT7 point reduced significantly. The treatment of naltrexone at high doses reduced the ethanol intake and low-dose injection of naltrexone in conjunction with the MAI also suppressed ethanol intake.

Conclusions

The results of the current study indicate that using the MAI at the HT7 point effectively reduces ethanol consumption in rats. Furthermore, the coadministration of the MAI and a low dose of naltrexone can produce some more potent reducing effect of ethanol intake than can acupuncture alone.

Repetitive Electroacupuncture Attenuates Cold-Induced Hypertension through Enkephalin in the Rostral Ventral Lateral Medulla

Acupuncture lowers blood pressure (BP) in hypertension, but mechanisms underlying its action are unclear. To simulate clinical studies, we performed electroacupuncture (EA) in unanesthetized rats with cold-induced hypertension (CIH) induced by six weeks of cold exposure (6 °C). EA (0.1 - 0.4 mA, 2 Hz) was applied at ST36-37 acupoints overlying the deep peroneal nerve for 30 min twice weekly for five weeks while sham-EA was conducted with the same procedures as EA except for no electrical stimulation. Elevated BP was reduced after six sessions of EA treatment and remained low 72 hrs after EA in 18 CIH rats, but not in sham-EA (n = 12) and untreated (n = 6) CIH ones. The mRNA level of preproenkephalin in the rostral ventrolateral medulla (rVLM) 72 hr after EA was increased (n = 9), compared to the sham-EA (n = 6), untreated CIH rats (n = 6) and normotensive control animals (n = 6). Microinjection of ICI 174,864, a δ-opioid receptor antagonist, into the rVLM of EA-treated CIH rats partially reversed EA's effect on elevated BP (n = 4). Stimulation of rVLM of CIH rats treated with sham-EA using a δ-opioid agonist, DADLE, decreased BP (n = 6). These data suggest that increased enkephalin in the rVLM induced by repetitive EA contributes to BP lowering action of EA.

Manual acupuncture at the SJ5 (Waiguan) acupoint shows neuroprotective effects by regulating expression of the anti-apoptotic gene Bcl-2

Acupuncture at the SJ5 (Waiguan) acupoint has neuroprotective effects in cerebral infarction, but the underlying mechanism remains poorly understood. Here, we analyzed gene expression in healthy rat cerebellum using a pathway-focused DNA microarray to screen 113 genes associated with 18 signal transduction pathways. After 20 minutes of acupuncture at SJ5, the expression of Bcl-2 and Birc1b mRNA was markedly increased. This was confirmed by real-time reverse transcription PCR. Furthermore, western blot analysis showed that Bcl-2 protein expression remained high in the cerebellum until at least 2 hours after cessation of acupuncture. These findings indicate that acupuncture at SJ5 exerts neuroprotective effects by regulating the expression of anti-apoptotic gene Bcl-2.

What do we understand from clinical and mechanistic studies on acupuncture treatment for hypertension?

The outcome of acupuncture on hypertension treatment is inconclusive. This study aims to evaluate the influence of acupuncture on hypertension, based on findings from mechanistic studies over the course of decades particularly those conducted at the University of California, Irvine. Low-current and low-frequency electroacupuncture (EA) at P5-6 (overlying the median nerve) and S36-37 (overlying the deep peroneal nerve) reduced high blood pressure in a subset of patients (~70 %) with mild-to-moderate hypertension, in a slow-onset (4-8 weeks) but long-lasting (1-2 months) manner. EA inhibited cardiovascular sympathoexcitatory neurons through activation of neurons in the arcuate nucleus of the hypothalamus, the ventrolateral periaqueductal gray in the midbrain and the nucleus raphe pallidus in the medulla, through inhibiting the activity of premotor sympathetic neurons in the rostral ventrolateral medulla (rVLM). Several neurotransmitters such as glutamate, acetylcholine, opioids, GABA, nociceptin, serotonin and endocannabinoids were involved in this EA-induced hypotensive response. The long-lasting inhibition of hypertension induced by EA was related to opioids and GABA in the rVLM, neural circuitry between the arcuate and ventrolateral periaqueductal gray, and prolongation of the increase in preproenkephalin mRNA levels and enkephalin levels in the rVLM and arcuate. Moreover, the long-lasting inhibition of sympathetic activity by EA was confirmed in EA-treated hypertensive patients with decreased levels of norepinephrine, renin and aldosterone.

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.

Complementary therapy in polycystic ovary syndrome

Polycystic Ovary Syndrome (PCOS) is an endocrine disease. PCOS afflicts 5 to 10 % of women of reproductive age. The symptoms are: amenorrhea, oligomenorrhea, hirsutism, obesity, infertility, chronic hyperandrogenic anovulation and acne.

OTHER RISK FACTORS AGGRAVATE THIS CONDITION

insulin resistance, obesity, hypertension, dyslipidemia, inflammation and subclinical cardiovascular disease. Anxiety, depression and reduced quality of life are also common. This review highlights the mechanisms and the beneficial effects of acupuncture, exercise and resveratrol on animal models and on humans affected by PCOS.

Involvement of amygdaloid neuropeptide Y in the anxiolytic effects of acupuncture during ethanol withdrawal in rats

The role of neuropeptide Y (NPY) in the central nucleus of amygdala (CeA) in the preventive effects of acupuncture against ethanol withdrawal-induced anxiety was investigated. Rats were treated with 3g/kg/day of ethanol for 28 days, followed by 3 days of withdrawal. Bilateral acupuncture treatment at HT7 (Shen-Men), PC6 (Nei-Guan) or a non-acupoint was respectively added to the rats during the withdrawal once a day for three days. Enzyme-linked immunosorbent assays and real-time polymerase chain reaction analyses showed there was a significant decrease in NPY protein and mRNA expression in the CeA during ethanol withdrawal, which was reversed by acupuncture at HT7 but neither at PC6 nor at a non-acupoint. Acupuncture at HT7 also greatly inhibited the decrease in cAMP response element-binding protein (CREB) phosphorylation in the CeA. In elevated plus maze tests, a selective NPY Y1 receptor antagonist BIBP 3226 into the CeA before the acupuncture abolished almost completely the anxiolytic effect of acupuncture at HT7. These results suggest that acupuncture at HT7 rescues the depletion of amygdaloid NPY and reverses the decrease in CREB phosphorylation to produce anxiolytic effects during ethanol withdrawal.

Electroacupuncture modulation of reflex hypertension in rats: role of cholecystokinin octapeptide

Acupuncture or electroacupuncture (EA) potentially offers a nonpharmacological approach to reduce high blood pressure (BP). However, ~70% of the patients and animal subjects respond to EA, while 30% do not. EA acts, in part, through an opioid mechanism in the rostral ventrolateral medulla (rVLM) to inhibit sympathoexcitatory reflexes induced by gastric distention. CCK-8 opposes the action of opioids during analgesia. Therefore, we hypothesized that CCK-8 in the rVLM antagonizes EA modulation of sympathoexcitatory cardiovascular reflex responses. Male rats anesthetized with ketamine and α-chloralose subjected to repeated gastric distension every 10 min were examined for their responsiveness to EA (2 Hz, 0.5 ms, 1-4 mA) at P5-P6 acupoints overlying median nerve. Repeated gastric distension every 10 min evoked consistent sympathoexcitatory responses. EA at P5-P6 modulated gastric distension-induced responses. Microinjection of CCK-8 in the rVLM reversed the EA effect in seven responders. The CCK1 receptor antagonist devazepide microinjected into the rVLM converted six nonresponders to responders by lowering the reflex response from 21 ± 2.2 to 10 ± 2.9 mmHg (first vs. second application of EA). The EA modulatory action in rats converted to responders with devazepide was reversed with rVLM microinjection of naloxone (n = 6). Microinjection of devazepide in the absence of a second application of EA did not influence the primary pressor reflexes of nonresponders. These data suggest that CCK-8 antagonizes EA modulation of sympathoexcitatory cardiovascular responses through an opioid mechanism and that inhibition of CCK-8 can convert animals that initially are unresponsive to EA to become responsive.

Acupuncture effect and central autonomic regulation

Acupuncture is a therapeutic technique and part of traditional Chinese medicine (TCM). Acupuncture has clinical efficacy on various autonomic nerve-related disorders, such as cardiovascular diseases, epilepsy, anxiety and nervousness, circadian rhythm disorders, polycystic ovary syndrome (PCOS) and subfertility. An increasing number of studies have demonstrated that acupuncture can control autonomic nerve system (ANS) functions including blood pressure, pupil size, skin conductance, skin temperature, muscle sympathetic nerve activities, heart rate and/or pulse rate, and heart rate variability. Emerging evidence indicates that acupuncture treatment not only activates distinct brain regions in different kinds of diseases caused by imbalance between the sympathetic and parasympathetic activities, but also modulates adaptive neurotransmitter in related brain regions to alleviate autonomic response. This review focused on the central mechanism of acupuncture in modulating various autonomic responses, which might provide neurobiological foundations for acupuncture effects.

Acupuncture regulation of blood pressure: two decades of research

Although mechanisms underlying acupuncture regulation of pain have been studied by a number of laboratories in many countries, much less is known about its ability to modulate cardiovascular function. In the last two decades, our laboratory has systematically investigated the peripheral and central neural mechanisms underlying acupuncture regulation of blood pressure. These observations account for acupuncture's distant actions and, to some extent, its local actions, with respect to the site of needling. Four fundamental findings have advanced our knowledge. First, point-specific effects of acupuncture underlie its cardiovascular actions. Second, variable regions in the supraspinal and spinal central nervous system that receive input from somatic afferent stimulation account for acupuncture's ability to modulate blood pressure. Thus, depending on the underlying situation, for example, high or low blood pressure, acupuncture modifies autonomic outflow by reducing activity in brain stem nuclei that participate in the primary response. Third, repetitive acupuncture through a molecular mechanism can cause prolonged cardiovascular effects that far outlast acupuncture stimulation. Fourth, there is a range of cardiovascular responsiveness to acupuncture that depends, at least in part, on interactions between neural modulators that synaptically regulate autonomic function in the brain stem. Thus, acupuncture has the capability of profoundly regulating cardiovascular function in patients with disease, for example, hypertension, and the experimental laboratory is directing best approaches to study its actions in humans.

Repetitive electroacupuncture causes prolonged increased met-enkephalin expression in the rVLM of conscious rats

Enkephalinergic neurons in the rostral ventrolateral medulla (rVLM), an important presympathetic region in the brainstem, are activated by 30 min of low frequency (2 Hz) electroacupuncture (EA) at acupoints P5-P6, which overlie the median nerves. To more closely model the clinical application of acupuncture, we administered EA for 30 min twice over a 72 h period to unsedated conscious rats to examine its prolonged action. We hypothesized that repetitive EA would increase preproenkephalin mRNA and met-enkephalin in the rVLM of unsedated conscious rats. Rats received either EA (1-4 mA, 0.5 ms, 2 Hz) or sham stimulation (needle placement without electrical stimulation) twice at P5-P6 acupoints bilaterally. Preproenkephalin mRNA and its peptide met-enkephalin in the rVLM were measured 24 or 48 h after the final EA or sham procedure. Relative ratios of preproenkephalin mRNA levels (normalized with the 18S housekeeping gene) were almost doubled at 24h compared to sham (6.1 ± 0.79 vs. 3.1 ± 0.47). Met-enkephalin measured in rVLM tissue pooled from several rats exposed to the same treatment was increased by repeated EA by 68% after 24h and 51% after 48h, relative to sham. These findings suggest that repeated application of EA in the conscious rats enhances transcription and translation of enkephalin in rVLM for days. Since opioids in the rVLM contribute importantly to the action of EA on sympathetic outflow, this mechanism may contribute to the prolonged action of acupuncture on elevated blood pressure in patients.

Absence of actions of commonly used Chinese herbal medicines and electroacupuncture on myocardial infarct size

BACKGROUND

Some studies have suggested that certain Chinese herbal remedies and acupuncture could limit ischemia/reperfusion damage. We sought to determine whether the commonly used single herb Danshen (DS), either alone or in combination with Jiang Xiang (JX), or electroacupuncture (EA) reduces myocardial infarct size.

METHODS

An anesthetized rat model of proximal left coronary artery occlusion (30 minutes) and reperfusion (180 minutes) was used to measure infarct size (triphenyltetrazolium chloride) and ischemic risk zone (blue dye technique). Rats were either untreated (saline) or received an infusion of DS or DS + JX, starting 30 minutes prior to coronary occlusion. In a separate protocol, rats were untreated, received static needle (ND) placement without stimulation or EA at P5-P6 acupuncture points in the rat forearm starting 5 minutes before occlusion and lasting for 40 minutes, or starting 30 minutes before occlusion and lasting for 90 minutes.

RESULTS

In the herbal experiments, myocardial infarct size expressed as a fraction of the ischemic risk zone was 0.43 ± 0.06 in controls, 0.39 ± 0.05 in the DS group, and 0.42 ± 0.04 in the Danshen + JX groups (P = not significant [NS]). In the acupuncture study, there was no significant difference in infarct size as a fraction of the risk zone among the control group (0.38 ± 0.04), the ND group (0.47 ± 0.04), or the EA group (0.32 ± 0.05). When EA was started 30 minutes prior to coronary occlusion and continued for 30 minutes into reperfusion, infarct size was 0.41 ± 0.07 in controls and 0.38 ± 0.10 in EA (P = NS). Neither herbs nor EA altered heart rate or blood pressure. In a separate study of 5 minutes of coronary occlusion plus reperfusion, EA failed to reduce ventricular arrhythmias.

CONCLUSION

Our studies do not suggest a cardioprotective effect of DS or DS + JX or EA in an experimental model of myocardial ischemia/reperfusion.

Electroacupuncture and moxibustion decrease renal sympathetic nerve activity and retard progression of renal disease in rats

BACKGROUND/AIM

Chronic kidney disease (CKD) is an increasing major public health problem worldwide. The sympathetic nervous system and nitric oxide play an important role in the pathogenesis of CKD. Traditional Chinese medicine has accumulated thousands of years of therapeutic experiences. Electroacupuncture (EA) and moxibustion (MO) are two such therapeutic strategies. The aim of this study was to investigate the renal and hemodynamic effects of EA-MO in an experimental model of a CKD.

METHODS

Male Wistar rats submitted to 5/6th nephrectomy (5/6 NX) were studied for 8 weeks. There were four groups: (1) control, normal rats; (2) NX, 5/6 NX only; (3) NX-AS, 5/6 NX and EA-MO session using sham points, and (4) NX-AM, 5/6 NX and EA-MO session using real acupoints. Biochemical and blood pressure studies, renal sympathetic nerve activity measurements, nitric oxide levels and the histopathological indices were assessed.

RESULTS

The EA- and MO-treated group presented significant improvement in all measured functional and histopathological parameters.

CONCLUSION

These findings suggest that EA-MO had beneficial effects on CKD. This effect was probably achieved by the modulation of the renal sympathetic nerve activity and nitric oxide levels, leading to decreased blood pressure, which is associated with less proteinuria.

Neuroendocrine mechanisms of acupuncture in the treatment of hypertension

Hypertension affects approximately 1 billion individuals worldwide. Pharmacological therapy has not been perfected and often is associated with adverse side effects. Acupuncture is used as an adjunctive treatment for a number of cardiovascular diseases like hypertension. It has long been established that the two major contributors to systemic hypertension are the intrarenal renin-angiotensin system and chronic activation of the sympathetic nervous system. Recent evidence indicates that in some models of cardiovascular disease, blockade of AT1 receptors in the rostral ventrolateral medulla (rVLM) reduces sympathetic nerve activity and blood pressure, suggesting that overactivity of the angiotensin system in this nucleus may play a role in the maintenance of hypertension. Our experimental studies have shown that electroacupuncture stimulation activates neurons in the arcuate nucleus, ventrolateral gray, and nucleus raphe to inhibit the neural activity in the rVLM in a model of visceral reflex stimulation-induced hypertension. This paper will discuss current knowledge of the effects of acupuncture on central nervous system and how they contribute to regulation of acupuncture on the endocrine system to provide a perspective on the future of treatment of hypertension with this ancient technique.

Endogenous opiates and behavior: 2010

This paper is the thirty-third consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2010 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

An arcuate-ventrolateral periaqueductal gray reciprocal circuit participates in electroacupuncture cardiovascular inhibition

Electroacupuncture (EA) suppresses elevated blood pressure (BP) by activating the arcuate nucleus, ventrolateral periaqueductal gray (vlPAG), and inhibiting cardiovascular sympathetic neurons in the rostral ventrolateral medulla. This study investigated the reciprocal neural circuit between arcuate and vlPAG during EA inhibition of reflex increases in blood pressure. In α-chloralose anesthetized cats the gallbladder or splanchnic nerve was stimulated to induce cardiovascular sympathoexcitatory reflexes. Electrophysiological recordings showed that EA facilitates the arcuate neural response to splanchnic nerve stimulation. Bilateral vlPAG microinjection of D,L-homocysteic acid (DLH) facilitated the arcuate response to splanchnic nerve stimulation, while microinjection of kainic acid blocked EA (P 5-6 acupoints on pericardial meridian, overlying the median nerves) excitation of arcuate neurons. Retrograde microsphere tracer labeling in the arcuate or vlPAG perikarya was found after respective microinjection of the tracer in the vlPAG or arcuate of rats, demonstrating reciprocal direct connections between the two nuclei. EA inhibition of reflex-induced BP elevation was blocked by injection of glutamate or cholinergic receptor antagonist, kynurenic acid or atropine, into the arcuate. Excitation of vlPAG neurons during EA was blocked by arcuate microinjection of glutamate NMDA and non-NMDA receptor antagonists, AP-5 and CNQX, or the cholinergic receptor antagonist, atropine. Microinjection of DLH or acetylcholine (ACh) into the arcuate facilitated EA excitation of vlPAG neurons. Microinjection of AP5 and CNQX, but not atropine, into the vlPAG blocked EA excitation of arcuate neurons. Thus, a reciprocal excitatory glutamatergic neural circuit between the arcuate and vlPAG contributes to long-lasting EA cardiovascular inhibition. ACh in the arcuate but not in the vlPAG participates in the reciprocal excitation.

Neural mechanism of electroacupuncture's hypotensive effects

EA at P 5-6 and S 36-37 using low current and low frequency may be able to reduce elevated blood pressure in a subset of patients (∼70%) with mild to moderate hypertension. The effect is slow in onset but is long-lasting. Experimental studies have shown that EA inhibition of cardiovascular sympathetic neurons that have been activated through visceral reflex stimulation is through activation of neurons in the arcuate nucleus of the hypothalamus, vlPAG in the midbrain and NRP in the medulla, which, in turn, inhibit the activity of premotor sympathetic neurons in the rVLM. The arcuate also provides direct projections to the rVLM that contain endorphins. Glutamate, acetylcholine, opioids, GABA, nociceptin, serotonin and endocannabinoids all appear to participate in the EA hypotensive response although their importance varies between nuclei. Thus, a number of mechanisms underlying the long-lasting effect of EA on cardiovascular function have been identified but clearly further investigation is warranted.

Electroacupuncture enhances preproenkephalin mRNA expression in rostral ventrolateral medulla of rats

Electroacupuncture (EA) causes prolonged suppression of reflex elevations in blood pressure for at least 60min in anesthetized preparations. Thus, EA can modify sympathetic outflow and elevated blood pressure through actions in a number of hind brain regions, including the rostral ventrolateral medulla (rVLM). Since our previous data show that the opioid system plays a role in EA-related prolonged inhibition of presympathetic neuronal activity in the rVLM, we postulated that EA increases preproenkephalin (PPE) mRNA in this region, possibly for prolonged periods of time. Under alpha-chloralose anesthesia, rats received EA (1-2mA, 2Hz, 0.5ms) at P5-P6 acupoints (overlying median nerves) or sham (needle placement without electrical stimulation) for 30min. PPE mRNA in the rVLM also was evaluated in control rats that received surgery but no EA, or sham treatment. 20min, 1.5h or 4h following EA or sham treatment, PPE mRNA in the rVLM was analyzed by reverse transcription and quantitative real-time PCR. Relative ratios of PPE mRNA levels (normalized with 18s house keeping gene) were increased 1.5h after EA stimulation (7.77+/-1.39, n=6) relative to sham (2.84+/-0.37, n=5) but were unchanged both 20min and 4h after EA, compared to the sham or surgery groups at the same time points. Thus, 30min of EA transiently stimulates the production of enkephalin in a region of the brain that importantly regulates sympathetic outflow suggesting that even a single brief acupuncture treatment can increase the expression of this modulatory neuropeptide.