[Mechanisms of Acupuncture for Inflammatory Pain]

Although acupuncture, especially electroacupuncture (EA) is widely used to treat pain, its mechanisms have not been completely understood. In the present paper, we review the development of researches on the underlying mechanisms of EA in relieving inflammatory pain in recent years from a)peripheral inflammation-mediated immune response and neuro-immune interaction of receptors on primary nociceptors, b) crosstalk of neurotransmitters or neuromodulators, cellular signaling pathways, other related bioactive molecules, as well as glial activation in the dorsal horns of spinal cord, and c) supraspinal modulation of both sensory and affective components of pain. Inflammatory pain involves complex neuro-immune networks of neurons and non-neurons, various inflammatory mediators, neurotransmitters, neuromodulators and cellular signaling molecules in the peripheral and central nervous systems. Therefore, the analgesic mechanism of acupuncture still needs to be studied in depth at multi-levels and multi-targets, for instance, the reciprocal actions of peripheral opioid peptide, adenosine and TRPV 1 (which have been demonstrated to be involved in EA analgesia individually), the roles of spinal cord adenosine A 1 receptor (A 1 R) and A 2 R (for which fewer studies have been conducted), the interactions of classical neurotransmitters/neuromodulators/neuropeptides and their receptors, changes of intracellular molecules at transcriptional and translation levels, etc. during acupuncture analgesia. Furthermore, the mechanisms underlying reciprocal actions of neurotransmitters, neuromodulators and their receptors complicated in acupuncture-induced relief of pain affection in the higher brain regions also need to be explored further.