Abstract
It is generally known that acupuncture analgesia is not always observed in all individuals. In this study, the effectiveness of acupuncture analgesia was examined by measuring tail-flick latency of rats. A significant increase (P<0.05) of tail flick latency was observed in about half of the examined rats. Accordingly, animals were classified into an acupuncture effective group and a non-effective group by this criterion.
In another experiment, it was found that acupuncture effective animals (n=10) contained more endogenous morphine-like factors (MLF) in whole brain except cerebellum than acupuncture non-effective animals (n=9) . The contents of MLF unit in acupuncture effective animals were 25 times greater than those of acupuncture non-effective animals. The close correlation between individual acupuncture effectiveness and the individual amount of MLF (in the brain) was obtained and its coefficient of correlation was 0.71. No correlation was observed between pain threshold in normal state and the contents of MLF in the brain, and also any difference was not observed in the contents of opiate receptor in various parts of the brain between acupuncture effective and non-effective animals
Above results indicate that the individual variation in effectiveness of acupuncture analgesia might be attribute to that in contents of brain MLF.
