Effects of subchronic exposure to benzo[ɑ]pyrene on memory function and mRNA expressions of NMDA receptors in different brain regions in rats

Abstract

BackgroundThe altered expressions of hippocampal N-methyl-D-aspartate (NMDA) receptors induced by benzo[ɑ]pyrene (BaP) causes short-term spatial learning and memory impairment in humans and animals, but whether BaP causes alterations of NMDA receptor subunits in other brain regions and the associated neurotoxic mechanism is still essentially unknown. ObjectiveTo observe the mRNA expressions of NR1, NR2A, and NR2B of NMDA receptor subunits in different brain regions in SD rat model with subchronic exposure to BaP, and to provide a basis for in-depth study of the mechanism of BaP-induced neurotoxicity. MethodsForty male SD rats were selected and randomly divided into a control group and 1.00, 2.50, and 6.25 mg·kg−1 BaP exposure groups with 10 rats in each group. The exposure rats received intraperitoneal injection of BaP every other day for 90 d.The average latency to platform, the average total distance, and the duration spent in previous quadrant were measured by the Morris Water Maze. Real-time fluorescence quantitative PCR was used to detect the mRNA expressions of NR1, NR2A, and NR2B in hippocampus, cortex, cerebellum, and striatum of rats. ResultsThe average latency to platform and the average total distance in the 2.50 and 6.25 mg·kg−1 BaP groups were significantly prolonged compared with the control group (P0.05). ConclusionSubchronic BaP exposure can cause short-term spatial learning and memory impairment in rats, which may be related to the down-regulation of mRNA expressions of NR1, NR2A, and NR2B in hippocampus, changes of mRNA expressions of NR1, NR2A, and NR2B in cortical area, and the down-regulation of NR2B mRNA expression in cerebellum.

Keywords

• benzo[ɑ]pyrene
• rat
• spatial learning and memory ability
• n-methyl-d-aspartate receptor
• subunit