Abstract: OBJECTIVE:To explore the effects of paraquat (PQ) on blood-brain barrier and cognitive,learning and memory-related functions in rats.METHODS:SPF grade SD male rats were randomly divided into three groups:control (normal saline),low dose PQ exposure (1 mg/kg) and high dose exposure (10 mg/kg) groups.There were 15 rats per group and PQ was injected intraperitoneally for 6 weeks at 2 times a week.After the exposure,5 rats in each group were randomly selected for the Evans blue brain penetration test to detect the permeability of the blood-brain barrier.The remaining 10 rats in each group were subjected to behavioral experiments for their cognitive,learning,and memory abilities,including Morris water maze test,platform test,and shuttle box test.RESULTS:Compared with the control group,the content of Evans blue increased in the brain tissue of each dose group,the difference was statistically significant (P < 0.05).Morris water maze results show that the trajectories of rats in the 1 and 10 mg/kg PQ groups were more complex than those in the control group.With the increase of training days,the escape latency of each group was gradually shortened.The shortening trend of the 10 mg/kg PQ group was significantly lower than that of the control and the low dose groups (P < 0.05).During the test period,the number of crossings in the 1 and 10 mg/kg PQ group was significantly reduced compared with the control group (P < 0.05).The results of the platform test show that the memory latency of the 1 and 10 mg/kg PQ group was significantly lower than that of the control group,and the number of errors was significantly higher than that of the control group,and the number of errors in the 10 mg/kg PQ group was significantly higher than that in the 1 mg/kg PQ group (P < 0.05).The results of the shuttle box experiment show that the number of conditional responses in the two dose groups was significantly lower than that in the control group,and the number of errors was significantly higher than that in the control group (P < 0.05).CONCLUSION:Both 1 and 10 mg/kg doses of PQ damaged the blood-brain barrier and increased its permeability which in turn reduced cognitive,learning and memory functions.

Key words: paraquat, blood-brain barrier, cognitive memory function, rats