Effect of the ifenprodil administered into rostral anterior cingulate cortex on pain-related aversion in rats with bone cancer pain

BACKGROUND To assess the effect of rostral anterior cingulate cortex (rACC) administration with ifenprodil (NR2B receptor blocker) on bone cancer pain (BCP)-related aversion sentiment using the conditioned place avoidance experiments in rats. METHODS A total of 30 male Wistar rats without place preference were randomly assigned to three groups: control group (Group C, n = 10), BCP group (Group P, n = 10) and ifenprodil group (Group Ifen, n = 10). Three microliter MADB-106 cells were inoculated into right tibia bone marrow cavity in group P and Ifen, while the same dose of normal saline in group C as a control. Ifenprodil was administered into the rACC at the 14th day after inoculation in group Ifen and normal saline in group C and P. Mechanical stimulation pain thresholds of the rats' right hind paws were measured using Von Frey stimulation method at 1 day before injection of the tumor cells and at 3, 7,10, 12 and 14 days after the injection. The pain-related aversion in rats with BCP was determined by the conditioned place avoidance (CPA) test at 14 days after injection of ifenprodil. RESULTS The mechanical stimulation pain thresholds substantially decreased in rats in groups P and Ifen from 10 days to 14 days after the incubation with the MADB-106 cells (P < 0.05). There were significant differences in pain thresholds in groups P and Ifen compared to group C at 10, 12 and 14 days after inoculation (P < 0.05). The percentage of residence time in chamber A was (30 ± 4%) in group P, which was lower than (52 ± 5%) in group C (P < 0.05). After ifenprodil treatment, the percentage time in chamber A increased to (42 ± 5%), which was higher than that in group P and still lower than that in group C (P < 0.05). CONCLUSION Ifenprodil administered into rACC as a selective NR2B antagonist can effectively alleviate pain-related aversion sentiment in rats with BCP.