Neurophysiological basis of acupuncture-induced analgesia--an updated review.

Acupuncture is an ancient treatment modality that can trace its origins to as far back as 10,000 BC along the banks of the Yellow River in China. It involves the insertion of sharpened objects into specific areas of the body to achieve therapeutic effects. According to the theory of Traditional Chinese Medicine, acupuncture modulates the flow of Qi and Xue through the meridians so that the main organs (Zhongs-Fus) will re-establish homeostasis as governed by the laws of Yin-Yang and the Five Elements. In clinical practice, acupuncture is an efficacious treatment for alleviating acute and chronic pain, but a consensus on its underlying mechanisms is still lacking. This article presents an up-to-date review of the various neurophysiologic mechanisms that have been proposed to produce acupuncture-induced analgesia.