The Central Serotonergic System Mediates the Analgesic Effect of Electroacupuncture on <i>Zusanli</i> (ST36) Acupoints

Abstract

Evidence in the past decade indicates that the mechanisms of anti-nociception of electroacupuncture (EAc) involve actions of neuropeptides (i.e., enkephalin and endorphin) and monoamines (i.e., serotonin and norepinephrine) in the central nervous system. Our present results using a subcutaneous injection of formalin to test pain sensation in mice provide further understanding of the involvement of serotonin in the actions of EAc-induced analgesia. Our observations show that (1) EAc at three different frequencies (2, 10 and 100 Hz) elicited an anti-nociceptive effect as determined by behavioral observations of reduced hindpaw licking; (2) exogenously intracerebroventricular administration of 5-hydroxytryptamine (5-HT) exhibited an analgesic effect, which partially mimicked the analgesic actions of EAc; (3) the anti-nociception of EAc at different frequencies was attenuated after reduced biosynthesis of serotonin by the administration of the tryptophan hydroxylase inhibitor, p-chlorophenylalanine, and (4) the 5-HT_1A and 5-HT₃ receptor antagonists, pindobind-5-HT_1A and LY-278584, respectively, blocked three different frequencies of EAc-induced analgesic effects, but the anti-nociceptive effect of 100 Hz EAc was potentiated by the 5-HT₂ receptor antagonist, ketanserin. These observations suggest that 5-HT_1A and 5-HT₃ receptors partially mediate the analgesic effects of EAc, but that the 5-HT₂ receptor is conversely involved in the nociceptive response.

Effects of Electroacupuncture on Depression and the Production of Glial Cell Line–Derived Neurotrophic Factor Compared with Fluoxetine: A Randomized Controlled Pilot Study

“…The acupoints of DU20 and ST36 can rescue the imbalance of the 5-HT receptor, which is one of the major molecular causes of depression. [20][21] This finding provides a reliable basis for the treatment of depression. Interestingly, we observed a good curative effect in the acupuncture control group.…”

Effects of Acupuncture on the Symptoms of Anxiety and Depression Caused by Premenstrual Dysphoric Disorder

“…The hypothesis for this improvement is based on the supposition that the release of substances in the CNS, mainly 5-HT, [13][14][15] as a result of acupuncture, could have decreased symptoms because 5-HT dysfunction occurs in PMDD. 4 9 This present investigation is methodologically different from the previous study as it was a randomised clinical trial.…”

Spinal cholinergic mechanism of the relieving effects of electroacupuncture on cold and warm allodynia in a rat model of neuropathic pain

“…It is now viewed as an alternative method of medicine in Western countries [7,27]. Electroacupuncture (EA) is a modified acupuncture technique that, as its name implies, utilizes electrical stimulation, and its analgesic effects on different types of acute pains and persistent inflammatory pains have been shown in rodents and humans [2,4,20,28,35,49]. In the last 2 decades, several clinical studies have also reported the beneficial effects of acupuncture or EA on neuropathic pain [1,14,46].…”