| Objective Hg-expose could do harm to nervous system, TZC played an important role in brain development. TZC could protect central nervous system neurons from harmful effects of Hg. We found that TZC resisted the harmful effects of Hg by observing NOS activity, nNOS protein expression, in cortex and hippocampus of rats and by observing the abilities of learning and memory. We also observed the influence of TZC and Hg on nerve cell growth and synapse length of cultured cortex neurons, to study the mechanisms of TZC resisting the harmful effects of Hg. Method We divided 60 male Wistar rats (postnatal 21d) into 4 groups. Each group comprised 15 rats, including control group, Hg-exposed group (drink 4.3mg/kg.d choronic mercury). Others groups (drink 0.23 g/L, 0.46 g/L TZC) to intervene the harmful effects of Hg. We tested the rats' learning and memory behavior with Y-labyrinth after 75 days. 90 days later, we used NADPH-d histochemistry and ABC immunohistochemistry to measure NOS activity, nNOS protein expression in cortex and hippocampus.20 mice were divided into 4 groups randomly: normal control group, low Hg-exposed group, lower Hg-exposed group and TZC group. RT-PCR to measure the gene expressions of nNOS in brain tissue.By cortex neuron primary culture experimental technique, we observed different dosages of TZC (0.25×10-3mg/ml, 0.5×10-3mg/ml, 1.0×10-3mg/ml, 2.0×10-3mg/ml, 4.0×10-3mg/ml) and different dosages of choronic mercury (8×10-6mg/ml, 8×10-5mg/ml, 8×10-4mg/ml, 8×10-3mg/ml, 8×10-2mg/ml) which affected the growth, stock and synapse length in cultured cortex neurons. Result1. The results praxiology tests 75d's later, learning times of Y-labyrinth experiment were higher than that of control group (P<0.05). Because of the influenceof TZC, Hg-expose groups rats' learning times of Y-labyrinth experiment decreasedCPO.05).2. The results of NADPH-d histochemistry and nNOS immunohistochemistry75d's later, The NADPH-d positive neuron number in cortex, CAi subregion, CA3 subregion and dentate gyrus subregion of hippocampus of Hg-expose rats was higher than control group (P<0.05), the nNOS in CAi subregion, CAi subregion and dentate gyrus subregion of hippocampus of Hg-expose rats was lower than control group (P<0.05). the positive neuron's stain-intensity became weak and nerve fiber became short because of TZC, the positive neuron number in cortex, CAi subregion, CA3 subregion and dentate gyrus subregion of hippocampus increased significantly (PO.05), the positive neuron's stain-intensity toned up, nerve fiber grew. 3.Tbe results of RT-PCR Compared with the normal control group, the electrophoresis strip of the nNOS products of low Hg-exposed group were brighter than that of the control group and the relative content of nNOS mRNA was significantly increased (P<0.05y, The value of optical density of electrophoresis strip of the TZC group were higher than that of low Hg-exposed group and the relative content of nNOS mRNA was relatively increased (/^0.05);while lower Hg-exposed group were decreased than those of the low Hg-exposed group .(P>0.05). 4.The results of cortex neuron primary culture 8><10"6mg/ml choronic mercury could induce the growth activity of cultured cortex neurons to decrease while synapse length become short^O.OS). Along with the increase of the lead acetate concentration, the harmful effects on cultured cortex neuron also increased. 0.5x10'3mg/mI TZC could boost up cultured cortex neuron growth activity and the synapse growth (P<0.05), When the concentration of TZC reached 1.0><10'3mg/ml, the effect reached a peak. If the concentration of TZC reached 2.0x103mg/ml, the effects would decrease. In addition, 1.0><10"3mg/ml TZC could protect culturedcortex neurons from the harmful effects of Hg.Conclusion TZC could protect the central nervous system from the harmful effectsofHg.
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