[The role of central oxytocin in electroacupuncture analgesia]

The effects of intraventricular injection (ICV) of oxytocin (OT) and antioxytocin serum (AOTS) on the pain threshold and electroacupuncture (EA) analgesia in rats were investigated in this study. The potassium iontophoresis induced tailflick was used to measure the pain threshold. An increase of 20-38% in the pain threshold was observed within 80 min after OT injection (50 ng), while the OT administration (50 ng) in combination with EA produced a dramatic increase of 139-234% in the pain threshold, which was much higher than that in the saline-EA group (P less than 0.05 or 0.01). The OT effect was dose-related in the range between 25-100 ng. Although ICV of AOTS did not change the pain threshold, the EA analgesia became weakened significantly. After injection of AOTS, EA only produced an increase of 47-61% in the pain threshold, while following ICV injection of normal rabbit serum instead of AOTS the EA could cause a rise of 104-123% in the pain threshold. There was a significantly statistical difference between the above two groups (P less than 0.05-0.01). The data indicate that ICV of OT not only elevates the pain threshold, but also enhances the EA effect, and that AOTS attenuates the EA analgesia. These results suggest that endogenous oxytocin in the central nervous system may play a role in the electroacupuncture analgesia.