Objective: To explore the possible central and peripheral mechanisms of connexin 43 gene knockout in acupuncture analgesia.
Methods: Fifty-four wide type (WT) mice and 54 connexin 43 gene knockout (heterozygote, HT) mice were randomly divided into WT control group, WT model group, WT acupuncture group, HT control group, HT model group and HT acupuncture group (n = 18/group). Visceral pain model was established by intraperitoneal injection of 0.6% acetic acid (0. 1 mL/10 g). "Zhongwan" (CV 12) and bilateral "Zusanli" (ST 36) were punctured with filiform needles and stimulated for 30 min by manipulating the needle for 30 s every 5 min. The latency and the number of body-writhing response were observed and the contents of beta-endorphin (beta-EP) in hypothalamus and serum prostaglandin E2 (PGE2) were detected with radioimmunoassay (RIA).
Results: There was no significant difference in the latency and the number of body-writhing response, and contents of hypothalamic beta-EP and serum PGE2 between HT and WT control groups (P > 0.05). Compared with the corresponding control groups, the latency of body-writhing in WT model and HT model groups shortened significantly and the number of body- writhing increased considerably in two model groups (P < 0.01). While in comparison with WT model group, the latency of body-writhing prolonged significantly and the number of body-writhing decreased apparently in WT acupuncture group (P < 0.01); but no marked differences were found between HT model and HT acupuncture groups in these two indexes (P > 0.05). Compared with the corresponding control groups, the contents of both beta-EP and PGE2 increased obviously in WT model and HT model groups (P < 0.05). In comparison with WT model group, beta-EP levels in WT acupuncture group increased further significantly (P < 0.05), and serum PGE2 in WT acupuncture group decreased obviously (P < 0.05); but no significant changes were found between HT model and HT acupuncture groups in beta-EP and PGE2 levels (P > 0.05).
Conclusion: Acupuncture has a marked antinociceptive effect in WT mice with visceral pain, which may be related to its effects in increasing hypothalamic beta-EP and decreasing serum PGE2; while in connexin 43 gene knockout mice, all the above-mentioned effects of acupuncture are eliminated, indicating an important role of connexin 43 in the analgesic effect of acupuncture.