Effects of chronic benzoapyrene exposure on learning and memory and metabotropic glutamate receptor in rats

Objective To explore effects of chronic benzoapyrene (BaP) exposure on learning and memory and metabotropic glutamate receptor in rats.Methods Forty male Sprague-Dawley rats were randomly assigned to one of the five groups:blank control,solvent control,1.0,2.5,and 6.25 mg/kg·bw of BaP (8 mice in each group).The rats received intraperitoneal injection treatment for 13 weeks.Morris water maze was employed to test the learning and memory behavior.The expression of metabotropic glutamate receptor 1 (m GluR1),metabotropic glumate receptor 2 (mGluR2) in the hippocampus were detected with western-blot.Results Morris water maze test showed that the rats exposed 2.5 and 6.25 mg/kg·bw BaP had increased latencies (18.34±7.09 s and 24.0±12.76 s) (P<0.05 for all).The rats exposed to 6.25 mg/kg·bw BaP had prolonged time passing the aim target (22.14±14.96 s,P<0.01),decreased number of crossing platform (4.11±1.36) and swimming time in the target area (29.00±3.64 s,P<0.01)compared with the those of the rats in control and low-dose group.The results of western-bolt test demonstrated that the expression of mGluR1 and mGluR2 in the hippocampus of 6.25mg/kg·bw BaP(1.09±0.29 and 0.85±0.14) group were significantly higher than those of the control group (0.56±0.13 and 0.54±0.15 (P<0.05),while mGluR3 showed no statistically significant difference between the groups.Conclusion Chronic BaP exposure can lead to cognitive dysfunction and overexpression of mGluR1 and mGluR2,which may be one of the mechanisms of learning and memory impairment induced by BP.