The present study was conducted to evaluate the effect of electroacupuncture-(EAc-) induced antinociception (EAA) at different currents and frequencies in rat spinal cord. We found that naloxone (0.05 μ g i.t.) blocked EAA at different frequencies. Naltrindole (0.05 μ g i.t.) blocked EAA on the 7th day after EAc of 100 Hz. 5,7-Dihydroxytryptamine (100 μ g i.t.) significantly inhibited EAA at different frequencies on the 7th day after EAc. Pindobind (0.5 μ g i.t.), a 5-HT1A antagonist, notably attenuated EAA at different frequencies. Ketanserin (0.5 μ g i.t.), inhibited EEA at a lower frequency (<10 Hz) than at a higher frequency (100 Hz). LY-278584 (0.5 μ g i.t.) significantly inhibited EAA at a higher frequency (100 Hz) on the 7th day after EAc. The direction of effect of 8-OH-DPAT, on EAA was dependent on dosage. It had an inhibitory effect at a low dose (0.5 μ g i.t.) and a high frequency (100 Hz) but enhanced EAA at a higher dose at lower frequencies (<10 Hz). DOI (10 μ g, i.t.), did not affect EAA. These data indicate that the mechanism of EAA involves opioid receptors, and the serotonergic system, particularly, μ -, δ -opioid and 5-HT1A, 5-HT3 receptors and it is also dependent on the EAc frequency.