Despite the use of acupuncture to treat a number of heart diseases, little is known about the mechanisms that underlie its actions. Therefore, we examined the influence of acupuncture on sympathoexcitatory cardiovascular responses to gastric distension in anesthetized Sprague-Dawley rats. Thirty minutes of low-current, low-frequency, (0.3-0.5 mA, 2 Hz) electroacupuncture (EA), at P 5-6, S 36-37, and H 6-7 overlying the median, deep peroneal, and ulnar nerves significantly decreased reflex pressor responses by 40, 39, and 44%, respectively. In contrast, sham acupuncture involving needle insertion without stimulation at P 5-6 or 30 min of EA at LI 6-7 acupoints overlying the superficial radial nerve did not attenuate the reflex. Similarly, EA at P 5-6 using 40- or 100-Hz stimulation frequencies did not inhibit the reflex. Compared with EA at P 5-6, EA at two sets of acupoints, including P 5-6 and S 36-37, did not lead to larger inhibition of the reflex. Two minutes of manual acupuncture (MA; 2 Hz) at P 5-6 every 10 min for 30 min inhibited the reflex cardiovascular pressor response by 33%, a value not significantly different from 2-Hz EA at P 5-6. Single-unit afferent activity was not different between electrical stimulation (ES) and manual stimulation. However, 2-Hz ES activated more somatic afferents than 10- or 20-Hz ES. These data suggest that, although the location of acupoint stimulation and the frequency of stimulation determine the extent of influence of EA, there is little difference between low-frequency EA and MA at P 5-6. Furthermore, simultaneous stimulation using two acupoints that independently exert strong effects did not lead to an additive or a facilitative interaction. The similarity of the responses to EA and MA and the lack of cardiovascular response to high-frequency EA appear to be largely a function of somatic afferent responses.

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 ϭ 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 Ͼ1 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. somatic afferents; electroacupuncture; visceral afferents; rostral ventral lateral medulla; prolonged neuronal inhibition ALTERNATIVE MEDICINE is used with increasing frequency in the United States and most other countries. In particular, manual acupuncture and the potent alternative, electroacupuncture (EA), are used primarily for treatment of chronic ailments, including cardiovascular disease. Chinese and ...

Acupuncture and electroacupuncture (EA) have been used in traditional Chinese medicine to treat a wide range of diseases and conditions, including angina pectoris and myocardial infarction. In a feline model of reflex-induced reversible myocardial ischemia, electrical stimulation of the median nerves to mimic EA (Neiguan acupoint) significantly improved ischemic dysfunction, secondary to an inhibitory effect of EA on reflex pressor effects evoked by bradykinin (BK). The central mechanism of EA’s inhibitory effect in this model is unknown. Accordingly, in α-chloralose-anesthetized cats, BK (10 μg/ml) was applied to the gallbladder to elicit a cardiovascular reflex response that significantly ( P < 0.05) increased arterial blood pressure and heart rate; normalized systolic wall thickening (%WTh) of the left ventricle, measured by ultrasonic single-crystal sonomicrometer, increased by 31 ± 11% ( P < 0.05). After ligation of a side branch of the left anterior descending coronary artery, the reflex pressor response to BK resulted in a significant decrease of %WTh (−32 ± 6%) in the ischemic region. When bilateral EA of the Neiguan acupoints was performed, the pressor response to BK was inhibited and regional myocardial function was significantly improved (+19 ± 20%). The inhibitory effects of EA on blood pressure and %WTh were reversed by intravenous injection of naloxone (0.4 mg/kg; n = 9) or microinjection of naloxone (10 nM in 0.1 μl/site; n= 14) into the rostral ventrolateral medulla (rVLM). Thus %WTh with intravenous naloxone was reduced to −13 ± 29% ( P<0.05) during stimulation of the gallbladder. Our results indicate that the inhibitory effect of EA on the BK-induced pressor response and the consequent improvement of ischemic dysfunction is dependent on the activation of opioid receptors, specifically receptors located in the rVLM.

Li P, Tjen-A-Looi SC, Guo Z, Fu L, Longhurst JC. Long-loop pathways in cardiovascular electroacupuncture responses. J Appl Physiol 106: 620 -630, 2009. First published December 12, 2008 doi:10.1152/japplphysiol.91277.2008.-We have shown that electroacupuncture (EA) at P 5-6 (overlying median nerves) activates arcuate (ARC) neurons, which excite the ventrolateral periaqueductal gray (vlPAG) and inhibit cardiovascular sympathoexcitatory neurons in the rostral ventrolateral medulla (rVLM). To investigate whether the ARC inhibits rVLM activity directly or indirectly, we stimulated the splanchnic nerve to activate rVLM neurons. Micropipettes were inserted in the rVLM, vlPAG, and ARC for neural recording or injection. Microinjection of kainic acid (KA; 1 mM, 50 nl) in the ARC blocked EA inhibition of the splanchnic nerve stimulation-induced reflex increases in rVLM neuronal activity. Microinjection of D,Lhomocysteic acid (4 nM, 50 nl) in the ARC, like EA, inhibited reflex increases in the rVLM neuronal discharge. The vlPAG neurons receive convergent input from the ARC, splanchnic nerve, P 5-6, and other acupoints. Microinjection of KA bilaterally into the rostral vlPAG partially reversed rVLM neuronal responses and cardiovascular inhibition during D,L-homocysteic acid stimulation of the ARC. On the other hand, injection of KA into the caudal vlPAG completely reversed these responses. We also observed that ARC neurons could be antidromically activated by stimulating the rVLM, and that ARC perikarya was labeled with retrograde tracer that had been microinjected into the rVLM. These neurons frequently contained ␤-endorphin and c-Fos, activated by EA stimulation. Therefore, the vlPAG, particularly, the caudal vlPAG, is required for ARC inhibition of rVLM neuronal activation and subsequent EA-related cardiovascular activation. Direct projections from the ARC to the rVLM, which serve as an important source of ␤-endorphin, appear also to exist. arcuate nucleus; ventrolateral periaqueductal gray; rostral ventrolateral medulla; D,L-homocysteic acid; kainic acid CARDIOVASCULAR DISEASE IS the greatest cause of death in middle-aged and elderly North Americans and Europeans. Although western science has developed a number of effective treatment strategies for this disease, treatment is not perfect and often is associated with side effects. As such, there has been increasing interest from the western countries in exploring alternative medicinal treatments and considering new therapies, such as acupuncture, for cardiovascular disease. According to the World Health Organization, acupuncture is effective in more than 40 medical conditions, including cardiac pain and hypertension (24). Experimental studies have shown that lowcurrent, low-frequency electroacupuncture (EA) employed over deep nerves, like P 5-6 (pericardial meridian) overlying the median nerve, effectively inhibits cardiovascular sympathoexcitatory reflexes and the rostral ventrolateral medulla (rVLM) presympathetic neuronal responses. Conversely, electrical stimulation ...

No abstract