Reflex modulation of visceral functions by acupuncture-like stimulation in anesthetized rats

Effect of Electroacupuncture at Different Acupoints on the Expression of NMDA Receptors in ACC and Colon in IBS Rats

Objective

To observe the effects of electroacupuncture (EA) at different acupoints on the expression of N-methyl-D-aspartate receptor (NMDA receptor ) and behaviors in irritable bowel syndrome (IBS) rats.

Methods

Wistar rats were randomly divided into blank control group (blank group, n=10) and model preparation group (n=50); experimental rat model of IBS was established by the “neonatal maternal separation and acetic acid enema” combined with “colorectal distension stimulation” method. A total of 50 IBS rats were randomly assigned to five groups of 10 each: model group, Yintang (GV29) group, Neiguan (PC6) group, Tianshu (ST25) group, and Zusanli (ST36) group. Rats in four treatment groups, aged 9 weeks old, were treated with EA by HANS with a sparse-dense wave with a frequency of 2/100 Hz, current of 0.1-0.3mA, and 20 min/stimulation, every other day for a total of 5 sessions. After treatment, the abdominal visceral sensitivity was evaluated by abdominal withdrawal reflex (AWR), and the psychological and emotional behavior of rats were evaluated by the open-field test (OFT). The expression of NMDA receptors in anterior cingulate cortex (ACC) was detected by Quantitative Real-time PCR, and the positive expression of NMDA receptors in colon was detected by immunohistochemistry.

Results

The IBS rat's abdomen is more sensitive and irritable; NR1, NR2A, and NR2B in ACC and NR1 and NR2B in colon of rats significantly increased in the model group versus the normal group (P<0.01) and were inhibited in all treatment groups (P<0.01, P<0.05). Additionally, NR2A and NR2B in ACC reduced more in GV29 group (P<0.01) than in other treatment groups (P all<0.05) compared with the model group. The expression of NR2B in colon was significantly inhibited in ST36 group (P<0.01) and inhibited in GV29 group and ST25 group (P all <0.05) compared with the model group. And the expression of NR2B in colon was more inhibited in ST36 group than in PC6 group (P<0.01).

Conclusions

EA at different acupoints could obviously relieve abdominal pain and abnormal behaviors in IBS rats in different degrees of effects. The effect of abdominal pain-relief, from greatest to least, is ST25, ST36, GV29, and PC6, while the effect of relieving abnormal behaviors caused by IBS, from greatest to least, is GV29, PC6, ST36, and ST25. There are significant differences in the expressions of NMDA receptors in ACC and colon among different acupoints. This difference should be related to the location distribution and indications of acupoints.

Effect of acupuncture on intestinal motility and related neural mechanisms

We review the literature about the effect of acupuncture on intestinal motility in recent 10 years and analyze the related neural mechanisms. In addition to the enhancing or inhibitory effect on intestinal movement, acupuncture can show a bidirectional modulatory effect on intestinal function. The neural mechanism related to acupuncture involves the central nervous system, the autonomic nervous system and the enteric nervous system. Most of acupuncture studies focused on the gastric motility, and there is a lack of studies on the intestinal motility. More acupuncture studies on intestinal motility should be conducted, and the quality of studies should be enhanced. Future research should pay attention to the central mechanism and the signal transduction pathways related to acupuncture.

Distal traditional acupuncture points of the large intestinal meridian and the stomach meridian differently affect heart rate variability and oxygenation of the trapezius muscle

Physicians in traditional Chinese medicine have found that acupoints and meridians have effects on specific parts of the body. The aim of this study was to see how acupressure at distal acupuncture points of a specific meridian affects heart rate variability (HRV) and oxygenation of the trapezius muscle. Forty-one female participants were randomly allocated to three groups. Subjects in the Stomach Meridian acupuncture point (ST) group received acupressure at ST 34, ST 36, and ST 41, subjects in the Large Intestinal Meridian acupuncture point (LI) group received acupressure at LI 4, LI 10, and LI 11, and subjects in the control group did not receive any stimuli. HRV and oxygenation of the trapezius muscles were measured. The high frequency components of HRV in the control and LI groups tended to be higher than those in the ST group. Total hemoglobin in the control and LI groups eventually reached significantly higher levels than in the ST group. While oxyhemoglobin (ΔO2Hb) in the control and LI groups did not change, ΔO2Hb in the ST significantly decreased temporarily.

Acupuncture and clomiphene citrate for live birth in polycystic ovary syndrome: study design of a randomized controlled trial

Acupuncture is an alternative therapy to induce ovulation in women with polycystic ovary syndrome (PCOS), but there is no study reporting the live birth rate following ovulation induction by acupuncture or its potential as an adjuvant treatment to clomiphene citrate (CC). We assess the efficacy of acupuncture with or without CC in achieving live births among 1000 PCOS women in Mainland China. This paper reports the methodology of an ongoing multicenter randomized controlled trial. The randomization scheme is coordinated through the central mechanism and stratified by the participating sites. Participants will be randomized into one of the four treatment arms: (A) true acupuncture and CC, (B) control acupuncture and CC, (C) true acupuncture and placebo CC, and (D) control acupuncture and placebo CC. To ensure the quality and integrity of the trial we have developed a unique multinational team of investigators and Data and Safety Monitoring Board. Up to the end of April 2013, 326 subjects were recruited. In conclusion, the success of this trial will allow us to evaluate the additional benefit of acupuncture beyond the first line medicine for fertility treatment in PCOS women in an unbiased manner.

Electrical vs manual acupuncture stimulation in a rat model of polycystic ovary syndrome: different effects on muscle and fat tissue insulin signaling

In rats with dihydrotestosterone (DHT)-induced polycystic ovary syndrome (PCOS), repeated low-frequency electrical stimulation of acupuncture needles restores whole-body insulin sensitivity measured by euglycemic hyperinsulinemic clamp. We hypothesized that electrical stimulation causing muscle contractions and manual stimulation causing needle sensation have different effects on insulin sensitivity and related signaling pathways in skeletal muscle and adipose tissue, with electrical stimulation being more effective in DHT-induced PCOS rats. From age 70 days, rats received manual or low-frequency electrical stimulation of needles in abdominal and hind limb muscle five times/wk for 4–5 wks; controls were handled but untreated rats. Low-frequency electrical stimulation modified gene expression (decreased Tbc1d1 in soleus, increased Nr4a3 in mesenteric fat) and protein expression (increased pAS160/AS160, Nr4a3 and decreased GLUT4) by western blot and increased GLUT4 expression by immunohistochemistry in soleus muscle; glucose clearance during oral glucose tolerance tests was unaffected. Manual stimulation led to faster glucose clearance and modified mainly gene expression in mesenteric adipose tissue (increased Nr4a3, Mapk3/Erk, Adcy3, Gsk3b), but not protein expression to the same extent; however, Nr4a3 was reduced in soleus muscle. The novel finding is that electrical and manual muscle stimulation affect glucose homeostasis in DHT-induced PCOS rats through different mechanisms. Repeated electrical stimulation regulated key functional molecular pathways important for insulin sensitivity in soleus muscle and mesenteric adipose tissue to a larger extent than manual stimulation. Manual stimulation improved whole-body glucose tolerance, an effect not observed after electrical stimulation, but did not affect molecular signaling pathways to the same extent as electrical stimulation. Although more functional signaling pathways related to insulin sensitivity were affected by electrical stimulation, our findings suggest that manual stimulation of acupuncture needles has a greater effect on glucose tolerance. The underlying mechanism of the differential effects of the intermittent manual and the continuous electrical stimulation remains to be elucidated.

Probable mechanisms of needling therapies for myofascial pain control

Myofascial pain syndrome (MPS) has been defined as a regional pain syndrome characterized by muscle pain caused by myofascial trigger points (MTrPs) clinically. MTrP is defined as the hyperirritable spot in a palpable taut band of skeletal muscle fibers. Appropriate treatment to MTrPs can effectively relieve the clinical pain of MPS. Needling therapies, such as MTrP injection, dry needling, or acupuncture (AcP) can effectively eliminate pain immediately. AcP is probably the first reported technique in treating MPS patients with dry needling based on the Traditional Chinese Medicine (TCM) theory. The possible mechanism of AcP analgesia were studied and published in recent decades. The analgesic effect of AcP is hypothesized to be related to immune, hormonal, and nervous systems. Compared to slow-acting hormonal system, nervous system acts in a faster manner. Given these complexities, AcP analgesia cannot be explained by any single mechanism. There are several principles for selection of acupoints based on the TCM principles: “Ah-Shi” point, proximal or remote acupoints on the meridian, and extra-meridian acupoints. Correlations between acupoints and MTrPs are discussed. Some clinical and animal studies of remote AcP for MTrPs and the possible mechanisms of remote effectiveness are reviewed and discussed.

'Forbidden points' in pregnancy: no plausible mechanism for risk

It has been suggested that acupuncture may pose particular risks during pregnancy: by enhancing oxygenation to the developing embryo (presumably via increasing blood flow to the uterus); by affecting the level of maternal progesterone in early pregnancy; or by stimulating uterine contractions. This article examines the proposed risks and fails to find any plausible physiological mechanism for them.

Spinal cord mechanism involving the remote effects of dry needling on the irritability of myofascial trigger spots in rabbit skeletal muscle

OBJECTIVE

To elucidate the neural mechanisms underlying the remote effects produced by dry needling rabbit skeletal muscle myofascial trigger spots (MTrSs) via analyses of their endplate noise (EPN) recordings.

DESIGN

Experimental animal controlled trial.

SETTING

An animal laboratory of a university.

ANIMALS

Male New Zealand rabbits (N=96) (body weight, 2.5-3.0kg; age, 16-20wk).

INTERVENTION

Animals received no intervention for neural interruption in group I, transection of the tibial nerve in group II, transection of L5 and L6 spinal cord in group III, and transection of the T1 and T2 spinal cord in group IV. Each group was further divided into 4 subgroups: animals received ipsilateral dry needling, contralateral dry needling, ipsilateral sham needling, or contralateral sham needling of gastrocnemius MTrSs.

MAIN OUTCOME MEASURES

EPN amplitudes of biceps femoris (BF) MTrSs.

RESULTS

BF MTrS mean EPN amplitudes significantly increased (P<.05) initially after gastrocnemius verum needling but reduced to a level significantly lower (P<.05) than the preneedling level in groups I and IV with ipsilateral dry needling or contralateral dry needling, and in group II with contralateral dry needling (but not ipsilateral dry needling). No significant EPN amplitude changes were observed in BF MTrS in group III or in the control animals receiving superficial needling (sham).

CONCLUSION

This remote effect of dry needling depends on an intact afferent pathway from the stimulating site to the spinal cord and a normal spinal cord function at the levels corresponding to the innervation of the proximally affected muscle.

Involvement of the mechanoreceptors in the sensory mechanisms of manual and electrical acupuncture

The modalities of acupuncture can be broadly classified into manual acupuncture (MA) and electroacupuncture (EA). Although MA has been reported to cause winding of tissue around the needle and subsequent activation of the sensory mechanoreceptors and nociceptors, the sensory mechanisms of acupuncture stimulation are not fully understood. To test the hypothesis that the involvement of the mechanoreceptors in the sensory mechanism is different in MA and EA, we examined the effects of a stretch-activated channel blocker gadolinium on the hemodynamic responses to hind limb MA and EA in anesthetized rats (n = 9). Gadolinium significantly attenuated the MA-induced bradycardic response (-22 ± 5 vs. -10 ± 3 bpm, P<0.05) and tended to attenuate the MA-induced depressor response (-30 ± 5 vs. -18 ± 4 mmHg, P = 0.06). On the other hand, gadolinium significantly attenuated both the EA-induced bradycardic (-22 ± 5 vs. -9 ± 4 bpm, P<0.01) and depressor responses (-32 ± 6 vs. -15 ± 5 mmHg, P<0.01). These results indicate that the mechanoreceptors are involved in the sensory mechanisms for both MA and EA.

Electroacupuncture induces Fos expression in the nucleus tractus solitarius via cholecystokinin A receptor signaling in rats

OBJECTIVES

Cholecystokinin, a satiety hormone, acts on cholecystokinin A receptor on vagal afferent neurons that project to the nucleus tractus solitarius, resulting in inhibition of feeding. Cholecystokinin is known to be released by electroacupuncture stimulation at certain body sites which elicits profound psychophysiological responses. Our previous study has revealed the involvement of cholecystokinin and cholecystokinin A receptor in the electroacupuncture stimulation-induced modulation of feeding. The aim of the present study was to examine whether electroacupuncture stimulation at the acupuncture point ST36 (Joksamni) activates the nucleus tractus solitarius neurons and whether such effect is mediated by cholecystokinin A receptor.

METHODS

Using an immunofluorescent analysis of Fos, a neuronal activation marker, we compared the Fos immunoreactivity of the nucleus tractus solitarius among three groups of Sprague-Dawley rats: (1) control (48 hour fasting + saline pre-treatment + no electroacupuncture stimulation); (2) SalEA (48 hour fasting + saline pre-treatment + ST36 electroacupuncture stimulation); (3) LorEA (48 hour fasting + pre-treatment of cholecystokinin A receptor antagonist, lorglumide + ST36 electroacupuncture stimulation).

RESULTS

ST36 electroacupuncture stimulation significantly reduced 30 minute food intake (p<0.05, SalEA versus control) and increased Fos expression in the nucleus tractus solitarius (p<0.01, SalEA versus control). The effects of electroacupuncture on food intake and Fos were blocked by a lorglumide pre-treatment (p>0.05, LorEA versus control).

DISCUSSION

Our finding suggests that ST36 electroacupuncture stimulation activates the nucleus tractus solitarius neurons via cholecystokinin A receptor signaling pathway, which may be the underlying central mechanism of electroacupuncture-induced satiety effect.

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.

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.

Effects of electroacupuncture on retinal nerve growth factor and brain-derived neurotrophic factor expression in a rat model of retinitis pigmentosa

The aim of this study was to investigate the effect of electroacupuncture (EA) on the progression of retinal degeneration in rats affected by inherited retinitis pigmentosa (IRP) and to correlate this event with the retinal expression of neurotrophins. Thirty-day-old Royal College of Surgeons (RCS) rats were exposed to 25-min-long daily sessions of low-frequency EA for 11 consecutive days. Control-untreated and EA-treated rats were sacrificed 1 h after the last EA session, and their retina removed for biochemical, molecular, and immunohistochemical analyses. Our data revealed that daily sessions of low-frequency EA for 11 days to RCS rats during a critical developmental stage of retinal cell degeneration cause an increase of retinal nerve growth factor (NGF) and NGF high-affinity receptor (TrkA) expression; and increase of outer nuclear layer (ONL) thickness; and enhanced vascularization. These findings suggest the possible beneficial effects of EA treatment in the development of IRP-like retinal degeneration of RCS rats and that the mechanism through which EA might exerts its action on the regulation of NGF and brain-derived neurotrophic factor (BDNF) and/or their receptors in retinal cells.

Role of unmyelinated fibers in electroacupuncture cardiovascular responses

The afferent fiber type responsible for the transmission of sensory neural traffic to the central nervous system during acupoint stimulation is uncertain. Several early studies evaluating compound action potentials have suggested that myelinated fibers contribute to the afferent input of the autonomic reflex adjustments during electroacupuncture (EA). Our more recent data, employing single unit recordings of somatic afferents, show that both myelinated and unmyelinated fibers are stimulated by EA, although more finely myelinated than unmyelinated fibers are activated by low frequency, low current stimulation. We hypothesized in this study that unmyelinated group VI fibers also contribute significantly to the inhibitory influence of EA on cardiovascular pressor responses. We found that neonatal capsaicin-treated rats depleted of substance P from primary afferents were insensitive to the inhibitory EA effect during gastric distention. Thus, EA at P5-P6 reduced gastric distention-induced pressor responses from 19+/-3 to 11+/-2 mmHg in eight untreated rats while capsaicin-treated rats (n=9) were unresponsive to EA. Substance P containing neurons in dorsal root ganglion cells at Ti-T5 were significantly decreased in the capsaicin-treated rats from 47+/-4 to 22+/-4 cells. Treated compared to untreated rats also demonstrated a significantly (P<0.03) reduced number of group IV fibers identified with single unit recording techniques. This study demonstrates that the inhibitory effect of EA at P5-P6 on cardiovascular autonomic excitatory reflexes involves unmyelinated group IV fibers of the median nerves.

Effect of electro-acupuncture on ovarian expression of alpha (1)- and beta (2)-adrenoceptors, and p75 neurotrophin receptors in rats with steroid-induced polycystic ovaries

BACKGROUND

Estradiol valerate (EV)-induced polycystic ovaries (PCO) in rats is associated with an increase in ovarian sympathetic outflow. Low-frequency (2 Hz) electro-acupuncture (EA) has been shown to modulate sympathetic markers as well as ovarian blood flow as a reflex response via the ovarian sympathetic nerves, in rats with EV-induced PCO.

METHODS

In the present study, we further tested the hypothesis that repeated 2 Hz EA treatments modulate ovarian sympathetic outflow in rats with PCO, induced by a single i.m. injection of EV, by investigating the mRNA expression, the amount and distribution of proteins of alpha1a-, alpha1b-, alpha1d-, and beta2-adrenoceptors (ARs), as well as the low-affinity neurotrophin receptor (p75NTR).

RESULTS

It was found that EV injection results in significantly higher mRNA expression of ovarian alpha1b- and alpha1d-AR in PCO rats compared to control rats. The p75NTR and beta2-ARs mRNA expression were unchanged in the PCO ovary. Low-frequency EA resulted in a significantly lower expression of beta2-ARs mRNA expression in PCO rats. The p75NTR mRNA was unaffected in both PCO and control rats. PCO ovaries displayed significantly higher amount of protein of alpha1a-, alpha1b- and alpha1d-ARs, and of p75NTR, compared to control rats, that were all counteracted by repeated low-frequency EA treatments, except for alpha1b-AR.

CONCLUSION

The present study shows that EA normalizes most of the EV-induced changes in ovarian ARs. Furthermore, EA was able to prevent the EV-induced up regulation of p75NTR, probably by normalizing the sympathetic ovarian response to NGF action. Our data indicate a possible role of EA in the regulation of ovarian responsiveness to sympathetic inputs and depict a possible complementary therapeutic approach to overcoming sympathetic-related anovulation in women with PCOS.

Skin temperature in the extremities of healthy and neurologically impaired children

Little emphasis has been accorded to peripheral skin temperature impairments in children with neurological disorders but attention has been paid to the significance of cold extremities (autonomic failure) for well-being and quality of life in adults stroke patients. Therefore, it seems important to investigate skin temperature in children with neurological disorder, especially when their communication is impaired. In the present study, we wanted to objectively verify any skin temperature differences between pre-school children with and without neurological disorders and also ascertain if any correlation existed between skin temperature and physical activity. Skin temperatures in 25 healthy children and 15 children with cerebral or spinal cord damages were assessed using infrared radiation. The temperatures were recorded on the palm and the dorsal surface of the hands and on the sole and dorsal surface of the feet three times at 15-minute intervals over 30min. A significant lower mean skin temperature in all measurement points was seen in non-walking children with cerebral damages compared to healthy controls. Also, the mean skin temperature was significantly lower in all foot measuring points in the children with cerebral damages that were unable to walk compared to those walking. In conclusion, as cold extremities may result in impaired well-being and hypothetically may be associated with other symptoms born by the child, further investigations of thermal dysfunction and autonomic function are of importance and treatment may be warranted.

Medullary substrate and differential cardiovascular responses during stimulation of specific acupoints

Electroacupuncture (EA) at P5-P6 acupoints overlying the median nerve reduces premotor sympathetic cardiovascular neuronal activity in the rostral ventral lateral medulla (rVLM) and visceral reflex pressor responses. In previous studies, we have noted different durations of influence of EA comparing P5-P6 and S36-S37 acupoints, suggesting that point specificity may exist. The purpose of this study was to evaluate the influence of stimulating P5-P6 (overlying the median nerve), LI4-L7 (overlying branches of the median nerve and the superficial radial nerve), LI6-LI7 (overlying the superficial radial nerve), LI10-LI11 (overlying the deep radial nerves), S36-S37 (overlying the deep peroneal nerves), or K1-B67 (overlying terminal branches of the tibial nerves) specific acupoints, overlying deep and superficial somatic nerves, on the excitatory cardiovascular reflex and rVLM responses evoked by stimulation of chemosensitive receptors in the cat's gallbladder with bradykinin (BK) or direct splanchnic nerve (SN) stimulation. We observed point-specific differences in magnitude and duration of EA inhibition between P5-P6 or LI10-LI11 and LI4-L7 or S36-S37 in responses to 30-min stimulation with low-frequency, low-current EA. EA at LI6-LI7 and K1-B67 acupoints as well as direct stimulation of the superficial radial nerve did not cause any cardiovascular or rVLM neuronal effects. Cardiovascular neurons in the rVLM, a subset of which were classified as premotor sympathetic cells, responded to brief (30 s) stimulation of the SN as well as acupoints P5-P6, LI10-LI11, LI4-L7, S36-S37, LI6-LI7, or K1-B67, or underlying somatic pathways in a fashion similar to the reflex responses. In fact, we observed a significant linear relationship (r(2) = 0.71) between the evoked rVLM response and reflex change in mean arterial blood pressure. In addition, EA stimulation at P5-P6 and LI4-L7 decreased rVLM neuronal activity by 41 and 12%, respectively, for >1 h, demonstrating that prolonged input into the medulla during stimulation of somatic nerves, depending on the degree of convergence, leads to more or less inhibition of activity of these cardiovascular neurons. Thus EA at acupoints overlying deep and superficial somatic nerves leads to point-specific effects on cardiovascular reflex responses. In a similar manner, sympathetic cardiovascular rVLM neurons that respond to both visceral (reflex) and somatic (EA) nerve stimulation manifest graded responses during stimulation of specific acupoints, suggesting that this medullary region plays a role in site-specific inhibition of cardiovascular reflex responses by acupuncture.

Ovarian blood flow responses to electro-acupuncture stimulation at different frequencies and intensities in anaesthetized rats

The purpose of the present study was to investigate changes in ovarian blood flow (OBF) in response to electro-acupuncture (EA) stimulation at different frequencies and intensities in anaesthetized rats. Whether the ovarian sympathetic nerves were involved in OBF responses was elucidated by severance of the ovarian sympathetic nerves. In addition, how changes in the systemic circulation affected OBF was evaluated by continuously recording blood pressure. OBF was measured on the surface of the left ovary using laser Doppler flowmeter. Acupuncture needles with a diameter of 0.3 mm were inserted bilaterally into the abdominal and the hindlimb muscles and connected to an electrical stimulator. Two frequencies-2 Hz (low) and 80 Hz (high)-with three different intensities-1.5, 3, and 6 mA-were applied for 35 s. Both low- and high-frequency EA at 1.5 mA and high-frequency EA at 3 mA had no effect on OBF or mean arterial blood pressure (MAP). Low-frequency EA at 3 and 6 mA elicited significant increases in OBF. In contrast, high-frequency EA with an intensity of 6 mA evoked significant decreases in OBF, followed by decreases in MAP. After severance of the ovarian sympathetic nerves, the increases in the OBF responses to low-frequency EA at 3 and 6 mA were totally abolished, and the responses at 6 mA showed a tendency to decrease, probably because of concomitant decreases in MAP. The decreased OBF and MAP responses to high-frequency EA at 6 mA remained after the ovarian sympathectomy, and the difference in the responses before and after ovarian sympathectomy was nonsignificant. In conclusion, the present study showed that low-frequency EA stimulation increases OBF as a reflex response via the ovarian sympathetic nerves, whereas high-frequency EA stimulation decreases OBF as a passive response following systemic circulatory changes.