Objective To explore the reasonable dosage of zinc
supplementation for intervention with the sub-clinical patients and study
the effect of zinc
supplementation at different dosage on brain structure and function and their mechanism.Methods The change of
learning and memory function and the activity of NOS(nitride oxide synthase)in different sub-unit of hippocampus in rats were observed by Y-lost-palace test and NADPH-d histochemistry.Results Zinc supplementation at low but adequate dosage(200 mg/kg zinc in forage)could improve the learning and memory function by increasing the activity of NOS in hippocampus construction and sub-regions of CA1 and CA3 and dentate gyrus of rats.Zinc supplementation with excessive dosage within a limit(400 mg/kg zinc in forage)hadn't obvious curative effect.Excessive zinc supplementation beyond the limit(≥600 mg/kg zinc in forage)could impair the learning and memory ability and decrease the activity of NOS in hippocampus of rats.All of these might be one of the main mechanisms that excessive zinc supplementation beyond the limit could interfere with the learning and memory function.Conclusion Zinc supplementation at lower dosage can improve the learning and memory function of rats.Zinc supplementation at an excessive dosage can impair it.The changes of NOS activity in hippocampus may be one of the mechanisms of zinc affecting the learning and memory.