In order to explore the analgesic effect of melatonin and its influence on acupuncture analgesia

the present study was designed to investigate the effect induced by intraperitoneal (i.p.) melatonin (30

60

120 mg/kg) and melatonin (60 mg/kg) combined with electroacupuncture in rats. Antinociception was determined by tail flick lantency (TFL) to hot water at 50 ℃. The results showed that 30 mg/kg melatonin could not influence the TFL

but 60 and 120 mg/kg melatonin could prolong the TFL

moreover

the change (%) of TFL which induced by 120 mg/kg melatonin was greater than that induced by 60 mg/kg. During melatonin combined with electroacupuncture

the change (%) of TFL was much greater than using electroacupuncture or melatonin (60 mg/kg) alone. It is suggested that melatonin has analgesic effect and it can enhance the effect of electroacupuncture analgesia.