Alterations in rat central nervous system endorphins following transauricular electroacupuncture

Auricular electro-stimulation (electroacupuncture) was found to produce naloxone-reversible analgesia in the rat. These behavioral effects were accompanied by significant increases in cerebrospinal fluid (CSF) levels of endorphins with concomitant decreases in the basomedial hypothalamus and medial thalamus of beta-endorphin-like immunoreactivity as well as endorphin-like radioreceptor activity. In addition, the radioreceptor assay also revealed a decrease in endorphin-like radioreceptor activity in the periaqueductal gray (PAG) matter. These results are interpreted to imply that electroacupuncture in the rat produces at least part of its analgesic action by activating central nervous system endorphinergic circuitry which results in a release and depletion of endorphins in certain brain loci and a concomitant elevation in the CSF. Hypophyseal endorphins do not appear to be involved in mediating acupuncture-induced analgesia in the rat since plasma levels of endorphins were not altered by this manipulation.