Effect Of Benzo "a" Pyrene On Learning Behaviors And Nmdar2b.bdnf.creb1 And P300 In Hippocampus Of Weaned Rats

Objective: To observe the changes about pathohistology and neurobehavior of the rats induced by benzo [a] pyrene (B [a] P) and to investigate the changes and mechanism of learning and memory in rats by different doses of benzo [a] pyrene.Methods: Forty weaned rats (28 days) were randomly divided into five groups: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 (30 d). The capability of learning and memory in rats were measured by Morris water maze test, and the BDNF,NMDAR2B,CREB1 and p300 content in hippocampus were tested by immunohistochemistry.Results:(1) In training of Morris water maze,the average escape latency was extended gradually with increasing dose, and there is a statistically significant difference between high-dose group and the control group(P﹤0.01). Residence time of the original platform phenomenon is no significant difference among five groups, (P> 0.05). (2) In control group the morphosis of mice hippocamp pyramidal layer neuron is basically normal,lining up in order. (3) Immunohisto- chemical results:plenty of immune reaction positive neurons can be seen in hippocamp pyramidal layer,CREB1 and NMDAR2B positive reaction islocated in cell membrane,BDNF and P300 positive reactions mainly localized in the cytoplasm.With the higher B[a]P exposed,the lower immune reaction positive neurons.The P300's immunore activity show increasing tendency with the increased dose of B[a]P exposed.Conclusion: Sub-acute B[a]P exposure did not obvious impair the morphology and structure of hippocampal neuron. But it can reduced spatial learning and memory in weaning rats ,which may be related to decreased levels of BDNF,CREB1,NMDAR2B in Hippocampus.