Alzheimer's disease (AD) is closely associated with impaired insulin signaling in brain, suggesting it to be a brain-specific form of diabetes and thus termed as the "type 3 diabetes". Metformin is one of the most widely used agent against insulin resistance. The present study aimed to investigate the therapeutic effect of metformin on memory retention in streptozotocin (STZ)-induced model of AD in rats using an inhibitory avoidance learning. Materials and Methods: In this experimental study,

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... male Wistar rats were randomly allocated into 7 groups: control; STZ-treated, STZ plus saline or metformin. For the induction of AD, STZ (3 mg/kg) was administered bilaterally into lateral ventricles. All rats were trained in shuttle box for inhibitory avoidance learning. Metformin (50, 100, 200 mg/kg, i.p) or saline were injected immediately after the training. The retention test was performed after two days. Results: The results showed that post-training injection of metformin dose-dependently increased the time spent in the light chamber before entering to the dark chamber in STZ-treated rats. Moreover, metformin dose-dependently improved the memory retention in the rats. Conclusion: Post-training injection of metformin dose-dependently enhanced the memory retention in STZ-induced model of AD.