Objective: To clarify effect of electroacupuncture (EA) on relieving chronic visceral pain and the underlying neurobiological mechanism for such an effect, we observed the effect of EA on the Irritable bowel syndrome (IBS) rat and then examined spinal expression of N-methyl-D-aspartate (NMDA) receptor-1 in rats. Methods: Daily mechanical colon distention was performed on male Sprague-Dawley neonatal rats to produce IBS model. EA was applied at acupoints of Zusanli (ST 36) and Shangjuxu (ST 37) in each hind leg. Abdominal withdrawal reflex (AWR) assessment or rectus abdominis electromyograms (AEMG) recordings were then performed after EA treatment. The mRNA expression of the NMDA subtype of glutamate receptors in the spinal dorsal horn (L4-5) before and after EA was investigated by RT-PCR analysis in IBS rats. Results: The results demonstrated that EA could significantly decreased both AWR scores from behavioral test and AEMG discharges from electrophysiological recording in IBS model rats elicited by colorectal distension (CRD) stimuli with strengths of 20, 40, 60 and 80 mmHg, respectively (P<0.05). Meanwhile there was a significant decrease in mRNA expression of NMDA receptor-1 in the spinal dorsal horn of IBS rats treated by EA (P<0.05), but no such effect was observed in IBS rats treated by sham EA (inserting needles without electrical stimulation). Conclusion: These results indicate that EA can relieve chronic visceral hyperalgesia in IBS rats and this effect might be correlated with the down-regulation of NMDA receptor- 1 in the dorsal horn of the spinal cord.