Objective To observe the effect of MK-801(non-competitive NMDA receptor antagonist) on NMDA1A RmRNA of the spinal cord and brainstem in morphine withdrawal rats. Methods Thirty-two rats were divided into four groups (n=8): control group, dependence group, withdrawal group and MK-801 group. The rats were killed 1 hour after naloxone challenge. The expression of NMDA 1A RmRNA was determined by methods of RT-PCR. Results The expression of NMDA 1A RmRNA in the spinal cord (0.84±0.16) and brainstem (0.74±0.14) significantly increased in morphine dependent group than in the control group (0.65±0.15) and (0.55±0.12) (P<0.05) and increased to a great higher extent in morphine withdrawal group (1.09±0.20) and (0.98±0.17) (P< 0.05 ). The expression of NMDA1A RmRNA in the spinal cord (0.78±0.18) and brainstem (0.69±0.14) of MK-801 group was lower than that of morphine withdrawal group (P<0.01).Conclusion MK-801 significantly inhibits the expression of NMDA1A RmRNA of central nerves system in morphine withdrawal rats.