OBJECTIVEThe present study aimed to test whether exposure to benzo(a)pyrene [B(a)P] affects spatial learning and short-term memory by modulating the expression of the Gria1 and Grin2a glutamate receptor subunit genes in the hippocampus.

METHODSThirty-six 21-24-day-old, male rats were randomly assigned into high-, medium-, and low-dose toxin exposure groups (6.25, 2.5, and 1 mg/kg, respectively) and a control group, each containing nine rats. The behavioral performance of adult rats exposed to sub-chronic administration of B(a)P was monitored by learning and memory tests (Morris water maze). Real-time PCR assays were used to quantify Gria1 and Grin2a gene expression in the hippocampus.

RESULTSAt medium and high doses, B(a)P impaired spatial learning performance. The crossing-platform-location frequency and the time spent swimming in the platform area, which both relate to short-term memory, were significantly decreased in B(a)P-treated rats compared with controls. The level of Gria1 mRNA increased 2.6-5.9-fold, and the level of Grin2a mRNA increased 10-14.5-fold, with a greater fold increase associated with higher doses of B(a)P.

CONCLUSIONWe demonstrated that sub-chronic administration of B(a)P inhibits spatial learning and short-term memory, and increases Gria1 and Grin2a expression in the hippocampus. This suggests a relationship of B(a)P exposure levels with Gria1 and Grin2a expression and impairment of short-term and spatial memory.