Cognitive Impairment And Expression Of GFAP In Diabetes Rats And The Influence Of The Insulin Therapy

Objective:To investigate cognitive impairment and astrocytes reaction in diabetic rats and the influence of the insulin therapy, through the behavior changes and GFAP reaction.Methods:52 health grown-up male SD(Sprague-Dawley) rats divided into 2 big groups stochastically: 1 month group (n=26) and 3 month group (n=26); Each group then divided into 3 groups stochastically: diabetic model group (n=10), insulin treatment group (n=10) and control group (n=6). Streptozotocin-induced diabetic model rat (60mg/kg) was established. In the insulin treatment group, the rats were treated with isophane insulin everyday(2-3U/day) based on blood glucose concentration. In order to maintain the blood glucose in a stable level, all rats' blood glucose concentration was measured 2 times every week at fixed time. Tests of Morris water maze were taken place 1 month and 3 months later respectively. After the Morris water maze tests, slices taken from hippocampus,basal ganglia,the white matter nearby lateral ventricle and frontal lobe were used to immunohistochemistral tests. The expression of GFAP positive cells was observed in diabetic rats.Results:1.Spatial study and memory ability estimate. Compared with control group, (1)The swimming incubation period of diabetic group including both 1 month and 3 month group was prolonged (P<0.05).(2) Insulin treatment group:the change of swimming incubation period in 1 month group not significant, while in 3 month group the swimming incubation period was prolonged(P<0.05).2.The expression of GFAP positive cells. Control group: GFAP positive cells in 3 month group in basal ganglia and white matter nearby lateral ventricle were more than that in 1 month group (P<0.05). (1)Compared with control group, we observed increased number of GFAP positive cells and tumescent cell body in diabetic group. The change of GFAP expression in different sites of brain was not significant in 1 month diabetic group. In 3 month diabetic group, the number of GFAP positive cells increased in basal ganglia (P<0.05) and white matter nearby lateral ventricle(P<0.05). (2)Compared with control group, the change of GFAP expression in different sites of brain was not significant in both 1 month and 3 month insulin treatment group, as well as that in 1 month diabetic group. In 3 month diabetic group, the number of GFAP positive cells decreased in basal ganglia(P<0.05) and white matter nearby lateral ventricle(P<0.05).Conclusion:1.Diabetic rats present learning and memory dysfunction at 1st month.2.The astrocytes change doesn't appear with early cognitive impairment in diabetic rats, suggesting cognitive impairment is not caused by astrocytes change. The astrocytes reactive proliferation which has regional selectivity can be found in long-term diabetes (3 months).3.The early insulin application in diabetic rats can delay the impairment of cognitive function, but with the development of diabetes mellitus, the insulin treatment can't prevent the occurrence of cognitive impairment in diabetic rats.