Abstract： Objective To investigate the effects of benzo[a]pyrene (B[a]P) exposure on the behaviors and hippocampal oxidative stress and ATPase in rats and the molecular mechanism of neurobehavioral toxicity of B[a]P.Methods A total of 120 male SD rats (21 days old) were randomly and equally assigned to five groups:blank control group,vegetable oil (solvent control) group,and 2.5,5,and 10 mg/kg B[a]P exposure groups.The rats in B [a]P exposure groups were injected intraperitoneally with B[a]P once a day for 4 consecutive weeks.Then,Morris water maze and shuttle box were used to evaluate the learning and memory abilities of rats; colorimetric assay was used to measure the activities of superoxide dismutase (SOD),Na+/K+-ATPase,and Ca2+/Mg2+-ATPase and the content of malonaldehyde (MDA) in the hippocampus; the concentration of Ca2+ in the hippocampus was measured by fluorescent labeling.Results Compared with the blank control group and solvent control group,the B[a]P exposure groups exhibited significant increases in escape latency,active avoidance response latency,and passive avoidance response latency and significant decreases in number of platform crossings and active avoidance response frequency in the last test (P＜0.05 for all comparisons),with a dose-effect relationship.In addition,the B[a]P exposure groups had significantly lower activities of SOD,Na+/K+-AT-Pase,and Ca2+/Mg2+-ATPase and significantly higher MDA level and Ca2+ concentration than the blank control group and solvent control group (P＜0.05 for all comparisons),with a dose-effect relationship.Conclusion The neurobehavioral toxicity of B[a]P may be related to increased oxidative stress and decreased activities of Na+/K+-ATPase and Ca2+/Mg2+-ATPase in the hippocampus of rats.