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 nonneurons

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.