Effects Of Short-term Benzo[a]pyrene Exposure On Neurobehavior In Mice

Objective:To observe the effects of short-term benzo[a]pyrene exposure on learning&memory and emotional neurobehavior in mice,and the morphological changes of neurons in the hippocampus of the brain,and to explore the mechanism of benzo[a]pyrenemic neurotoxicity.Methods:Forty C57BL/6 mice were randomly divided into a control group(0 mg/kg)and three BaP exposed groups(0.8 mg/kg、2 mg/kg、5 mg/kg).There are 10 mice in each group.Different dose of BaP was given to C57BL/6 mice by intraperitoneal injection every other day,the control group was treated with vegetable oil solvent for parallel treatment.After four weeks,the effects of subacute exposure to benzo [a] pyrene on learning&memory and anxiety-like behavior in mice were observed by sucrose preference test,open field test,elevated plus maze experiment and Y-maze test;Golgi staining was used to observe the changes of dendritic spine length,branching,and dendritic spine density of hippocampal C A1 and DG neurons.SPSS20.0 was used to analyze the experimental data.The experimental data were in accordance with the normal distribution.One-way ANOVA was used to compare the experimental results among different treatment groups,and the LSD and Dunnett T3 test was used to compare the two groups.P <0.05 considered that the difference was statistically significant.Results:Sucrose preference test showed that there was no statistical difference in the percentage of sucrose preference between groups.The results of Y-maze test showed that the time and frequency of explore the new arm in medium and high dose of benzo [a] pyrene group were significantly lower than that of the control group(P<0.05).The results of open-field test showed that there was no difference in the total distance of movement between mice exposed to benzo[a]pyrene and the control group.The movement distances in the peripheral area of the mice in the benzo[a]pyrene medium and high-dose groups were greater than that in the control mice.The mice in the medium and high doses of benzo[a]pyrene had fewer entry times in the center of the mice than in the control mice;The mice in the benzo[a]pyrene high dose group had less residence time in the center of the mice than in the control mice;the differences were statistically significant(P<0.05).The results of the elevated plus-maze test showed that the number of entry into the open arm and the time to stay in the open arm of the benzo[a]pyrene medium and high dose groups were all lower than those in the control group,and the percentage of retention time in the open arm was significantly lower than that in the control group(P<0.05).The percentage of the number of entry into the open arm of the medium and high doses groups were not significantly different from that of the control mice,but it was decreased(P>0.05).Golgi staining showed that the total length of dendrites,the number of dendritic branches,and dendritic spine density of hippocampal CA1 and DG neurons in high-dose group were all significantly lower than that in the control group(P<0.05).Conclusion:Behavioral results suggest that short-term exposure benzo[a]pyrene can cause changes in learning&memory dysfunction and anxiety-like behavior in mice;morphological observations suggest that short-term exposure benzo[a]pyrene can reduce total length of dendritic,number of dendritic branches and dendrite spine density of the neurons in hippocampal CA1 and DG.In summary,the short-term exposure benzo[a]pyrene caused changes in learning&memory dysfunction and anxiety-like behavior in mice,which may be related to the plasticity change of dendrites and dendritic spines in hippocampal CA1 and DG neurons.