Effects of methylmercury exposure on nerve-action in mice at fetal period and adult period

Objective: To investigate the changes of nerve-action in mice under methylmercury (MMC) exposure in one unit at fetal period and at adult period. Methods: 44 mice (C57BL/6Cr) were divided into four groups: control group, exposure group at fetal period (prenatal group), exposure group at adult period (adult group), and expsoure group at fetal period and adult period (repeative exposure group). Every group included 11 mice. The mice in prenatal group were given 3 mg · kg^-1 MMC for 3 d during days 12-14 gestation. The offsprings were given 12 mg · kg^-1 MMC when they when they were 13 weeks old in adult group. The mice were given MMC both at fetal period and adult period in repeative exposure group, while the same dose of physiological salt solution was given in control group. 10 d after administration of MMC at adult period, Open-field and Morris water-maze nerve action and brain path-histological test were performed. Results: In Open-field test, the inportamt index moving distance of appraise nerve action had a marked decrease in prenatal group, however, there was a increase in adult group, there was a significant difference between two groups (P<0.05); there was no nerve action change in repeative exposure group. In Morris water-maze test, there was significant difference between prenatal group and adult group (P<0.05). The repeative exposure group had a similar result with the prenatal group. The influence of exposure after growing had no meanings in statistics. The pathological results indicated that the mitochondria and globus palidus of pallium had lots of denaturalize neurocytes. Conclusion: Repeative methylmercury exposure in both fetal and grown-up period mice does not aggravate the influence on nerve-action; the damage on the brain of fetal mice may have compensative influence if it is damaged again after grow up.