BACKGROUND:Diet can regulate gene expression via manifesting genetic style so as to make a correlation with senility and tumor onset of tissue organs.OBJECTIVE:To observe the effect of diet quantity on learning and memory ability and immunological function changes in mice and verify the correlation between functional changes and diet quantity.DESIGN:Completely randomized grouping design.SETTINGS:Three Gorges University Medical College;School of Medicine,Hubei Institute for Nationalities.MATERIALS:Eighty Kunming mice of 3 weeks old,grade Ⅱ,weighing 17 - 18 g and either gender,were selected from Animal Experimental Center,Tongji Medical College,Huazhong University of Science and Technology.The experimental animals were disposed according to ethical criteria.At one week after feeding,they were randomly divided into 4 groups,including over-diet group,quantitative-diet group,quantitative-limit diet group and over-limit diet group with 20 mice in each group.METHODS:The experiment was carried out in the Medical Experimental Center of Hubei Institute for Nationalities and the Department of Laboratory,Central Hospital of Hubei Enshi Autonomous Prefecture from April to June 2006.① Diet quantity of animals was ＞ 6 g/d in the over-diet group,4 g/d in the quantitative-diet group,3.34 g/d in the quantitative-limit diet group and 1.8 g/d in the over-limit diet group,respectively.Mice in the four groups drank freely.②At 35 days after feeding,every 10 mice were randomly selected from each group and enclosed in the wide mouthed bottle (250 mL,containing sodalime) to observe and record survival time under normal pressure and hypoxic condition.Other mice were given step down test,shuttle box test and autonomic activity test.Step down test:The first step-down latency and error times within 5 minutes were used to evaluate learning ability and the memory ability was retested at 24 hours later.Shuttle box test:The shuttle-box latency and error times within 5 minutes were used to evaluate learning ability and the memory ability was retested at 24 hours later.Times of autonomic activity within 5 minutes were used to evaluate ability of autonomic activity.In addition,blood was collected from eyeball to measure plasma immune globulin and complement by using immunoturbidimetry.MAIN OUTCOME MEASURES:① Effect of different diet quantity on learning and memory ability;②effect of different diet quantity on times of autonomic activity and survival time under hypoxia and normal pressure;③ effect of different diet quantity on content of immune globulin and complement.RESULTS:All 80 mice were involved in the final analysis.① Effect of different diet quantity on learning and memory ability:There was no significant difference in learning ability during step down test (P＞0.05).While,memory ability in the over-diet group and the quantitative-diet group was better than that in the over-limit diet group (t=2.235 - 2.423,P＜0.05).During shuttle box test,learning and memory ability in the over-diet group was superior to that in the over-limit diet group (t =2.237 - 2.431,P＜0.05).While,memory ability in the quantitative-diet group and quantitative-limit diet group was superior to that in the over-limit group (t =2.704 - 2.813,P＜0.05).② Effect of different diet quantity on times of autonomic activity and survival time under hypoxia and normal pressure:There were significant differences in the times of autonomic activity among quantitative-diet group,quantitative-limit diet group and over-limit diet group (t=2.725 - 2.98,P＜0.05).Survival time in the quantitative-diet group and the quantitative-limit diet group was longer than that in the over-diet group (7=2.365,2.719,P＜0.05),but shorter than that in the over-limit diet group (t =2.427,2.538,P＜0.05).While,survival time in the over-limit diet group was longer than that in the over-diet group (t =2.765,P＜0.01).③Effect of different diet quantity on content of immune globulin and complement:There was no significant difference in content of IgG and IgA (P＞0.05).Content of IgM in the over-limit diet group was higher than that in the over-diet group,quantitative-diet group and quantitative-limit diet group (t=2.304 - 2.421,P＜0.05).Contents of complement C3 and C4 in the quantitative-diet group and quantitative-limit diet group were higher than those in the over-diet group (t=2.319 - 2.738,P＜0.05),but lower than those in the over-limit diet group (t =2.317 - 2.716,P＜0.05).While,contents of C3 and C4 in the over-limit diet group were higher than those in the over-diet group (t =3.247,4.53,P＜0.01).CONCLUSION:Both quantitative diet and quantitative-limit diet can improve learning and memory ability,autonomic activity and immnological stress;however,over-limit diet may decrease these abilities.