Objective To examine the effects of chronic manganese exposure on learning and memory and expression of brain-derived neurotrophic factor(BDNF) in rat, and explore whether plasma BDNF can be used as an effect biomarker of manganese exposure.
Methods Male Sprague-Dawley rats(n=40) were equally divided into 4 groups: control, low-, middle-, and highdose groups which received 0, 5, 10, and 20 mg/kg of manganese by intraperitoneal injection for 18 weeks, 5 d/week, respectively. Learning and memory was evaluated by Morris water maze task during six consecutive days at the 6th, 12th, and 18th weeks. The levels of plasma manganese and BDNF were detected by graphite furnace atomic absorption spectrometry(GFAAS) and ELISA kit, respectively.
Results Compared to the control, increases in escape latency and decreases in platform crossings of the high-dose group were noted at the 6th week(P< 0.05). Similarly, compared to the control, increases in escape latency and decreases in platform crossings of the middle-and high-dose groups were noted at the 12th and 18th weeks(both P< 0.05). Compared to the control group (13.16& #177;5.45) μg/L, the plasma manganese levels were higher in the low-, middle-, and high-dose groups (55.84& #177;11.62),(82.21& #177;8.26), and(115.58& #177;21.31) μg/L, respectively(all P< 0.05). Compared to the control group (232.64& #177;75.37) ng/L, the plasma BDNF levels were lower in the middle-and high-dose groups (145.80& #177;46.14) and(93.21& #177;44.92) ng/L, respectively(both P< 0.05). The plasma BDNF levels were positively correlated with the number of platform crossings, and negatively correlated with the escape latency and the plasma manganese levels(both P< 0.05).
Conclusion The rats treated with chronic manganese exposure may suffer deficits in spatial learning and memory and the down-regulated expression of plasma BDNF, suggesting that plasma BDNF might be an effect biomarker of manganese exposure.
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