Neurotrophic factors and cytokines are involved in the regulation of neuronal survival

axonal myelination

and synaptic plasticity in both central nervous system(CNS) and peripheral nervous system(PNS).The members of the neurotrophic factor family include nerve growth factor(NGF)

brain derived neurotrophic factor(BDNF)

neurotrophin-3(NT-3)

and neurotrophin-4/5(NT-4/5).These molecules bind to two types of receptors: 1) tyrosine kinase receptors(TrkA

TrkB

TrkC) and 2) common neurotrophin receptor(p 75 NTR).The internalization and retrograde axonal transport of neurotrophin receptors are important for their signal transduction supporting neuronal survival

synaptic plasticity

and axonal myelination.In addition

a growing body of data suggests that neurotrophins are involved in the pathophysiologicl courses of inflammatory pain

neurodegenerative disease

and psychiatric diseases.Cytokines

including IL-1

IL-2

IL-6

and TNF-alpha

are important mediators of the immune response and play a key role in the diseases by acting on inflammatory immune cells

neuronal cells

muscle cells

and vessel cells.Interestingly

some cytokines(e.g.TNF-α

IL-2

TGF-β) are also able to regulate synaptic plasticity and affect CNS functions.The neurotrophins and cytokines release in response to various stimuli

such as electronic stimulation

or inflammation.This crosstalk from PNS to CNS is involved in the pathophysiology of many human diseases and may contribute to the effects of acupuncture.Based on our knowledge to neurotrophins and cytokines

we proposed the neurotrophin/cytokine hypothesis for the mechanism of acupuncture.This hypothesis may initiate the discussion on the possible roles of neurotrophins/cytokines in the therapeutic effects of acupuncture and shed light to the discovery of mechanism of acupuncture in the treatment of devastating diseases.