The Effect of Cholesterol and Simvastatin on Passive Avoidance Memory of Streptozotocin-Induced Diabetic Rats

Cholesterol has different effects on memory, and diabetes caused adverse effect on cognition. Since there is not enough evidence regarding the effect of cholesterol on memory of diabetic animals, the effects of cholesterol and simvastatin on the passive avoidance memory of diabetic rat were studied. The study was done on 60 male Wistar rats (180 ± 20g). Diabetes was induced by i.p. injection of 65 mg/kg streptozotocin. The animals in diabetic cholesterol, diabetic simvastatin and diabetic cholesterol-simvastatin groups, were treated by 2% cholesterol in diet, daily gavage of 5 mg/kg simvastatin, and concomitant treatment of cholesterol and simvastatin, respectively. The avoidance memory of the rats of each group was measured using shuttle box apparatus 4 weeks later. Also, the cholesterol level of hippocampus was measured. Diabetes had no effects on working memory, but reduced step through latency time during test session. Treatment by cholesterol, simvastatin and cholesterol-simvastatin improved passive avoidance memory in diabetic rats, especially in cholesterol-simvastatin group compared to non-treated diabetic control group. The cholesterol level of hippocampus increased in diabetic cholesterol-simvastatin group compared to other groups (p<0.05). Administration of cholesterol and simvastatin for four weeks protected the diabetic rats against diabetes-induced cognition impairment, yet their combination produced more improvement. Our data suggest that inhibition of endogenous cholesterol synthesis may improve memory of diabetic rats.