| Objective While Zn has an important role for the formation and maintenance of LTP, Pb is one of the most powerful nervous poisoners, which could interfere the function of hippocampus by perturbating the electricity physiological action of Zn and competiting or replacing Zn in hippocampus, deducing cognitive function impairment. We observed the resistance of Zn to the effects of Pb on the activity of NOS and the protein and gene expression of nNOS in rat hippocampus during the experiment, for studying the impaired principle of Pb on learning and memory and the protective principle of Zn from that impairment.Methods 84 wistar rats were divided into 7 groups randomly, then they were fed with two different dosages of ZnSO4 and TZC or Tau in feed respectively, and given 0.2% PbAc solution. During the period, we observed the growth of rats and measured the weight every week. Three months later, Y-labyrinth test was applied to studing the function of learning and memory, and we used NADPH-d histochemistry and ABC immunohistochemistry and RT-PCR to measure the activity of NOS and the levels of protein and gene expressions of nNOS in hippocampus. Resultsl.The results of increased weight: Except the high TZC+Pb group, the increased weight of the other experimental groups were lower than that of the control 0x0. 05). the increased weight of high ZnSO4+Pb group ^ high TZC+Pb group wereobviously higher than that of the Pb group (p<0. 05).2.The results of labyrinth test: Except the high ZnSO4+Pb group> low TZC+Pb group the learning times of the other experimental groups were higher than that of the control 0x0.05). The learning times of the high ZnSO4+Pb group> low TZC+Pb group were lower than that of the Pb group (p<0. 05).3.The results of NADPH-d histochemistry experiment: In CAi of hippocampus: Compared with the control, except the high ZnSO4+Pb group, low TZC+Pb group, the activity of NOS of the other experimental groups were obviously cut down (/KO. 05), accompaning with decreased response intensity and shorted nerve fiber; Compared with the Pb group, low ZnSO4+Pb group, high ZnSO4+Pb group, Tau+Pb group, low TZC+Pb group, the activity of NOS were significantly aggrandized (p<0. 05) .But no significant changes in CAa were observed (p>0.05). In dentate gyrus of hippocampus: Compared with the control, except the low TZC+Pb group, the activity of NOS of the other experimental groups were obviously lessened (p<0. 05) ; the activity of NOS of low ZnSO4+Pb group, high ZnSO4+ Pb group, low TZC+Pb group were obviously enhanced (p<0. 05). 4.The results of ABC immunity histochemistry method: In CAi: Compared with the control, except the low TZC+Pb group, the number of the nNOS positive neurons of the other experimental groups were obviously cut down(p<0. 05); Compared with the Pb group, the number of the NADPH-d positive neurons of low ZnSO4+Pb group, high ZnSO4+Pb group, low TZC+Pb group were obviously aggrandized (p<0. 05). There were no significant difference in CA3 among each experimental groups (p>0.05). In dentate gyrus: Compared with the control, except high ZnSO4 +Pb group, low TZC+Pb group, the number of the nNOS positive neurons of the other experimental groups were obviously lessened (p<0. 05) ; the number of the nNOS positive neurons of low ZnSO4+Pb group was higher than thecontrol (p<0. 05) ; Compared with the Pb group, the number of the nNOS positiveneurons of the other experimental group were evidently increased (p<0. 05).5.The results of RT-PCR: The electrophoresis strip of the nNOS products ofhippocampus of the Pb group, low ZnSO4+Pb group, Tau+Pb group, high TZC+Pbgroup were darker than that of the control(p<0.05). the value of optical density ofelectrophoresis strip in hippocampus of the high ZnSCX+Pb group, low TZC+Pbgroup were higher than that of the Pb group(p<0.05).Conclusions All results above suggested that the changes of the NOS activity andthe protein gene expressions of nNOS in hippocampal conformation and subregionsmight be one of the most important...
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