A study of Morris water maze and ultrastructure alteration of neural-vascular unit in early stage diabetic rat

Objective To investigate the alteration of learning and memory function and brain ultrastructure in early stage diabetic rats.Methods 45 male SD rats were divided into 3 groups:control group,diabetes group 1 and diabetes group 2.Diabetic rat models were made by injection of Streptozocin,diabetes group 2 was fed with high fat diet.After 5 weeks of diabetes,following detections were carried out: body weight and blood glucose measurment,Morris water maze experiment to test learning and memory function,and transmission electron microscope to observe ultrastructure alteration of hippocampus,frontal lobe and temporal lobe in rats.Results 5 weeks after diabetes,there was significant difference in body weight and blood glucose between diabetes groups and control group(P0.01).In Morris place navigation test,there were significant difference in swimming speed between diabetes group 2 and control group(P0.01),and there was also statistical difference in every diabetes group(P0.05).Under transmission electron microscope,degenerative changes of neurons of both diabetes groups in hippocampus and cerebral cortex were detected,with obvious swelling in end foot of astrocytes were noted;the cavities of capillaries became narrow;microglial cell attached to the abnormal neurons.Conclusions In Morris place navigation test,diabetic rats swam further distances due to their poor searching strategy.Their fast swimming speed was considered ineffective because of their unshortened latency.Neural-vascular unit in hippocampus and cortex of early stage diabetic rats was injured.Damage in the diabetes group with high fat diet was the most serious.