Role of NR2B in rostal anterior cingulate cortex in development of pain-related aversion in a rat model of bone cancer pain: siRNA technique

Abstract

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 3 μl(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 0.2 μl was injected into rACC in group LV-NR2B, and pGC-FU-siRNA negative recombinant lentivirus 0.2 μl 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 removed for detecting NR2B protein and mRNA expression by Western blot or real-time polymerase chain reaction. Results Compared with the baseline at 1 day before inoculation, the MWT was significantly decreased at 7, 14 and 21 days after inoculation, and the percentage of residence time in room A was decreased at 14 days after inoculation in NS and LV-NC groups (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). Conclusion Up-regulated expression of NR2B in rACC is involved in development of pain-related aversion in a rat model of bone cancer pain. Key words: Receptors, N-methyl-D-aspartate; Bone neoplasms; Pain; Emotions