Objective To evaluate the role of 2B subunit-containing NMDA receptors ( NR2B) in the rostal anterior cingulate cortex ( rACC) in development of pain-related aversion in a rat model of bone cancer pain using siRNA technique. Methods Forty-five healthy male Wistar rats, weighing 220-250 g, were divided into 3 groups ( n=15 each) using a random number table method: normal saline blank control group ( group NS) , NR2B-siRNA lentivirus group ( group LV-NR2B) and pGC-FU-siRNA lentivirus group (group LV-NC). A total volume of MADB-106 cells 3μl (4. 8×109 cells∕ml) was inoculated into the bone marrow cavity of the right tibia of rats. At day 2 after inoculation, NR2B∕siRNA recombinant lentivirus 0. 2μl was injected into rACC in group LV-NR2B, and pGC-FU-siRNA negative recombinant lentivirus 0. 2μl was injected into rACC in group LV-NC. The mechanical paw withdrawal threshold ( MWT) was measured at 1 day before inoculation and 3, 7, 14 and 21 days after inoculation. Conditioned place avoidance test was performed at 1 day before inoculation and 14 days after inoculation, and the percentage of residence time in room A was calculated. The rats were sacrificed at 21 days after inoculation and the rACC was re-moved for detecting NR2B protein and mRNA expression by Western blot or real-time polymerase chain re-action. Results Compared with the baseline at 1 day before inoculation, the MWT was significantly de-creased at 7, 14 and 21 days after inoculation, and the percentage of residence time in room A was de-creased at 14 days after inoculation in NS and LV-NC groups (P<0. 05), and no significant change was found in the parameters mentioned above in LV-NR2B group (P>0. 05). Compared with group NS, the MWT was significantly increased at 14 and 21 days after inoculation, the percentage of residence time in room A was increased at 14 days after inoculation, and the expression of NR2B protein and mRNA was down-regulated in group LV-NR2B ( P<0. 05) , and no significant change was found in the parameters men-tioned above in group LV-NC (P>0. 05). Conclusion Up-regulated expression of NR2B in rACC is in-volved in development of pain-related aversion in a rat model of bone cancer pain.