Acctylcholine (ACh) is the neuro transmitter which carliest emerges no matter in development of species or in evolution of individual. In some lower animalwhole sensory afferent nerve is cholinedergic

in advanced animals part ofnociceptive sensory neuroanatomic pathways is corresponding to ascending reti-cular exciting system. So it is possible that ACh is considered as one of impo-rtant neurotransmitters relating to acupuncture analgesia.