Nocistatin (NST) and nociception/orphanin FQ (OFQ) are peptides derived from the same precursor that play opposing roles in pain modulation. OFQ antagonizes morphine analgesia and electroacupuncture (EA)-induced antinociceptive effect. The present study investigates whether NST potentiates EA-induced antinociceptive effect and reverses chronic tolerance to EA in mice. Injection of NST (0.5, 5.0 and 50.0ng) intracerebroventricularly had no effect on basal thermal latency, but produced a dose-ependent potentiation of EA-induced antinociceptive effect in mice with the maximum response at 5.0ng. NST (5.0ng) partly reversed chronic tolerance to EA. These results suggest that NST in the brain might play roles in EA-induced antinociceptive effect and the development of chronic tolerance to EA in mice.