Selection of nutrients for prevention or amelioration of lead-induced learning and memory impairment in rats

Background: We carried out animal experiments based on the orthogonal design L8(2⁷) setting seven factors with two different levels of each and 10 groups of rats. The nutrients tested were tyrosine, glycine, methionine, taurine, ascorbic acid, thiamine and zinc.Objectives: The objective of this study was to explore the optimal combinations of nutrients for prevention or amelioration of lead-induced learning and memory impairment.Methods: Rats were supplemented with nutrients by gavage once a day in two experiments: one was simultaneous nutrient supplementation with lead acetate administration (800 mg l^-1) for 8 weeks (prophylactic supplementation) and the other was nutrient supplementation for 4 weeks after the cessation of 4 weeks of lead administration (remedial supplementation). Morris water maze was initiated at ninth week. Rats were terminated for assays of levels of Pb in blood, activities of superoxide dismutase (SOD) and nitric oxide synthase (NOS) in hippocampus, levels of nitric oxide (NO) in hippocampus and expressions of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and cyclic adenosine monophosphate (cAMP) response element-binding protein messenger RNA in hippocampus.Results: Results showed that in prophylactic supplementation, methionine, taurine, zinc, ascorbic acid and glycine were the effective preventive factors for decreasing prolonged escape latency, increasing SOD and NOS activities and NO levels in the hippocampus, respectively. On the other hand, in remedial supplementation, taurine was the effective factor for reversing Pb-induced decrease in activities of SOD, NOS and levels of NO.Conclusions: In conclusion, the optimum combinations of nutrients appear to be methionine, taurine, zinc, ascorbic acid and glycine for the prevention of learning and memory impairment, while taurine and thiamine appear to be the effective factors for reversing Pb neurotoxicity.