Researchers have measured that acupuncture on the external ear (auricular acupuncture) produces biochemical anti-inflammatory effects. In the study, researches note that auricular acupuncture affected both opioid mechanisms and cholinergic muscarinic mechanisms.
The researchers induced inflammation and edema in rats with an injection of an irritant while under anesthesia. Electroacupuncture was applied to ear acupuncture points and a marked decrease of inflammation was measured. The pain relieving and anti-edema effects of auricular acupuncture were disrupted with methyl atropine, which blocks peripheral muscarinic receptors. Naloxone, an opioid receptor blocker, did not antagonize the anti-inflammatory effects of the electroacupuncture. As a result, the researchers concluded that auricular acupuncture exerts its anti-inflammatory effects more significantly through cholinergic muscarinic mechanisms than through opioid pathways.
The researchers first tested for auricular acupuncture points on the ears of rats by measuring points of low impedance because low impedance is associated with the location of many acupuncture points. Once determined, the researchers applied bilateral electroacupuncture using 0.2mm X 13mm needles at 1mm depth. 4 Hz pulses of 0.45ms duration with alternating polarity were stimulated for 45 minutes. The sham acupuncture group received 0 mA and the verum electroacupuncture group received stimulation at 0.7 to 1.0mA.
Peripheral muscarinic receptors mediate the anti-inflammatory effects of auricular acupuncture. Wai Y Chung1,2, Hong Q Zhang1 and Shi P Zhang1. Chinese Medicine 2011, 6:3. doi:10.1186/1749-8546-6-3. 1 School of Chinese Medicine, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China. 2. School of Chinese Medicine and Health Care, The Chinese University of Hong Kong Tung Wah Group of Hospitals Community College, Homantin, Hong Kong, China.