Influence of protein intake in learning and memory capabilities and mammalian target of rapamycin expression in premature rats / 中华神经医学杂志

ABSTRACT

Objective To study the influence of protein intake in learning and memory capabilities and mammalian target of rapamycin (mTOR) expression in premature rats.Methods Premature rars were randomly divided into three groups after weaningpreterm standard protein group,preterm low protein group and preterm high protein group.After weaning,three groups were respectively fed with standard protein diets (18％ protein),low protein diets (8％ protein) and high protein diets (30％ protein) until the end of experiment.When rats were at the 6th and 8th weeks,they were performed Morris water maze test to assess the learning and memory abilities,and irnmunohistochemistry and Westem blotting were used to observe the mTOR distribution and mTOR protein expression in the hippocampus.Results At the age of 6 weeks,the escape latencies of the premature rats did not change significantly on the 3rd and 4th day of the experiment; the frequency of crossing the platform and the mTOR-positive cells in hippocampal CA1 and CA3 regions of each group showed no significant differences (P＞0.05).At the age of 8 weeks,the escape latencies in finding the platform were shortened with increased training times for premature rats; the frequency of crossing the platform of high-protein premature rats was significantly higher than that in the other two groups (P＜0.05); and the mTOR expression in the hippocampal CA1 and CA3 regions of high-protein premature rats was also significantly increased as compared with the other two groups (P＜0.05).High-protein premature rats at the age of 8 weeks had significantly higher frequency of crossing the platform and increased mTOR-positive cells in the hippocampal CA1 and CA3 regions than those at the age of 6 weeks (P＜0.05).Western blotting also indicated that the hippocampal mTOR protein expression was not significantly different in each group at 6 week-old; the mTOR expression of high-protein premature rats was significantly higher than that in the other two groups at the age of 8 weeks.Conclusions In the early growth and development process of the brain,mTOR activity might be inhibited in the premature birth rats,which can lead to impaired learning and memory abilities.After a long time of high protein nutritional intake,impaired learning and cognitive abilities of premature rats can get recovery,which may be associated with up-regulation ofmTOR expression.