Activity of opioid peptidergic system in acupuncture analgesia.

To study the relationship between the opioid peptidergic system (OPS) and acupuncture analgesia (AA), observations have been made both at presynaptic levels and receptor sites in our college since 1975. It was found that AA could be reversed by naloxone in rabbits and in man. The opioid peptide activity increased in human cerebrospinal fluid and in the perfusate from certain brain areas during AA, as revealed by radio-receptor assay. The results indicate that OPS takes an active part in AA. To study further the activity of OPS, experiments were done at the level of nerve cells on rabbits's central gray (PAG). By using multimicropipettes for extracellular recording and iontophoresis of drugs, it was found that opiates produced a naloxone reversible inhibition on the spontaneous discharge of certain neurones. Such neurones were distributed mostly in the ventral part of the PAG. Similar to iontophoretic opiates, electroacupuncture (EA) had an inhibitory effect on PAG neurones and the inhibition could be reversed by iontophoretic naloxone. A correlation existed between the effects of EA and opiates (P less than 0.0174). EA and opiates also showed similar inhibitory effect on nociceptive response of PAG neurones. It was postulated that acupuncture signals activate the brain OPS to exert a double control over the transmission of pain sensation in the PAG, i.e., to block the conveyance of nociceptive impulses at situ and at other relay stations through inhibitory systems. In addition to the PAG, most brain areas important in AA are interrelated to OPS, and the interaction between opioid peptides and opiate receptors in these areas perform an analgesic function as a whole.