[Analgesic effect of buccal acupuncture on acute arthritis in rabbits and underlying mechanisms].

OBJECTIVE: To observe the analgesic effect of acupuncture and to explore its central analgesic mechanism in rheumatoid arthritis rabbits.
 Methods: A total of 60 flap-eared white rabbits were randomly assigned into a normal control group (n=6), a model group (n=6), a body-acupuncture group (n=24), and a buccal acupuncture group (n=24). The later 2 groups were further randomly assigned into 0, 0.5, 1, and 2 h subgroups, with 6 cases in each group. The rheumatoid arthritis model was established by induction of egg-albumin. In the body acupuncture group, bilateral "Xiyan" and "Zusanli" were punctured for 15 s while in the buccal acupuncture group, acupuncture was applied to "Xi" for 15 s, with the needle retaining for 30 min. The pain threshold was detected with PL-200, taking struggle movements of rabbits as a measurement index, response latency from irradiation to struggling movements as the rabbit's pain threshold. The contents of β-endorplhin (β-EP) and cholecystokinin-8 (CCK-8) in cerebrospinal fluid were examined by radioimmunoassay.
 Results: Compared with the control group, pain threshold and CCK-8 levels decreased significantly (P<0.01) and the concentration of β-EP significantly increased (P<0.05) in the model group. The pain threshold in the body-acupuncture group and the buccal acupuncture group at 0 and 
1 h (P<0.05 or P<0.01) increased significantly, while the β-EP and CCK-8 contents in the body-acupuncture group and the buccal acupuncture group were significantly higher than those in the model group (P<0.01 or P<0.05). Both β-EP and CCK-8 contents in the buccal acupuncture group at 0 h were significantly higher than those in the body-acupuncture group (P<0.05).
 Conclusion: The analgesic effect of buccal acupuncture is superior to that of body-acupuncture. Both buccal acupuncture and body-acupuncture can effectively raise the pain threshold in acute arthritis rabbits, which is closely associated with their effects in the up-regulation of β-EP and CCK-8 contents in cerebrospinal fluid.