Effect of benzo (a) pyrene on learning behaviors and NMDAR2B and brain-derived neurotrophic factor in hippocampus of weaned rats

Objective To investigate the changes and mechanism of learning and memory in rats by different doses of benzo (a) pyrene (B(a)P). Methods Forty weaned rats (28 days) were randomly divided into control group (NS), solvent group ( vegetable oil) and three B (a) P dosage groups (the doses were 5,10 and 20 mg / kg body weight respectively ). And all rats were administrated intraperitoneally every other day to one month. The capability of learning and memory in rats were measured by Morris water maze test, and the brain-derived neurotrophic factor ( BDNF) and NMDAR2B content in hippocampus were tested by immunohistochemistry. Results In training of Morris water maze,the average escape latency was extended gradually with increasing dose, and there was a statistically significant difference between high-dose group((62. 78 ±47. 25 )s) and the control group((40.60±38.79)s)(P＜ 0.01). Compared with the control group(11.25 ±2.63), the number of crossplatform of high-dose group(4.33 ±2.08) was statistically reduced (P＜0.05). B(a)P at 10 and 20 mg/kg decreased NMDAR2B and BDNF expression in hippocampus of rats in immunohistochemistry. The level of NMDAR2B was (162.23 ±6.56) in the high-dose group and (150.38 ± 15.34) in the control group(P＜0.05);the expression level of BDNF was (163. 13 ± 8.09) in the high-dose group and (141.83 ± 13.37) in the control group(P＜ 0.05). Conclusion Subacute B(a)P exposure can reduce spatial learning and memory in weaning rats, it may be related to decreased levels of NMDAR2B and BDNF in hippocampus. Key words: Benzo(a)pyrene; Learning and memory; Hippocampus; NMDAR2B; Brain-derived neurotrophic factor