Objective To investigate the changes of neurobehavioral performance as well as neuronal dendrites and dendritic spine density in hippocampal CA1 region of mice with subacute benzoapyrene exposure (BaP).
Methods Forty-eight C57BL/6 mice were randomly divided into four groups receiving either olive oil (control group) or BaP at 0.8, 2.0, and 5.0 mg/kg (low, medium, and high dose groups) every other day for four weeks. The neurobehavioral changes of mice were observed by sucrose preference test, open field test, and elevated plus maze test. The before-and-after-treatment changes of neuronal dendrites and dendritic spine density in hippocampal CA1 region were observed by Golgi staining.
Results In the sucrose preference test, there was no significant difference in the percentage of sucrose preference among the four groups(93.71±0.99)%, (89.43±4.10)%, (89.72±1.23)%, and (84.04±5.88)%, respectively (P > 0.05). In the open field test, compared with the control groupresidence time, (73.94±29.30) s; frequency of entering central area, 28.00±13.33; distance in surrounding area, (7 655.69±2 392.45) mm, the mice in the high dose group had shorter residence time in central area(50.34±12.74) s, and the mice in the medium dose group and the high dose group showed a less frequency of entering central area (15.88±8.84 and 13.25±7.92) and a longer distance in surrounding area(9 688.23±1 382.15) mm and (9 926.83±1 477.06) mm (Ps < 0.05). In the elevated plus maze test, the frequency of entry into the open arms (5.88±1.96 and 5.63±2.97) and the percentage of time spent in open arms(18.38±5.25)% and (20.90±2.27)% of mice in the medium and high dose groups were smaller than those in the control group11.63±7.25, (39.80±8.37)% (P < 0.05). Golgi staining results showed that the total dendritic length(1 295.88±238.26) μm, number of dendritic branches (16.50±1.38), and dendrite spine density per 10 μm (3.20±0.79) in the hippocampal CA1 neurons of the high dose group were lower than those in the control group(1732.81±239.69)μm, 22.17±2.56, and 5.90±1.20, respectively.
Conclusion Subacute BaP exposure could induce anxiety-like behavior in mice, which may be related to the change of plasticity of neuron dendrites and dendritic spines in hippocampal CA1 region.
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