L-carnosine Improves Short-Term Spatial Recognition Memory and Passive Avoidance Learning and Memory in Streptozotocin-Diabetic Rats

Background and Objective: Diabetes mellitus (DM) affects synaptic plasticity in the hippocampus, leading to impairments in learning and memory. L-carnosine, an endogenous dipeptide, is reported to exhibit anti-diabetic and antioxidant effects. Therefore, this study was designed to evaluate its effect on learning and memory in diabetic rats. Materials and Methods: In the present study, male Wistar rats (n=32) were randomly divided into four groups: control, control treated with carnosine (100 mg/kg), diabetic, and diabetic treated with carnosine (100 mg/kg). Diabetes was induced by streptozotocin (STZ) at a dose of 60 mg/kg. L-carnosine was injected i.p. at a dose of 100 mg/kg one week after STZ injection for 8 weeks. Blood sample was taken from retro-orbital plexus before STZ injection and 4 and 8 weeks after STZ injection to measure blood glucose level. Passive avoidance and Y maze tests were done to assess learning and memory deficits. Results: After 8 weeks, diabetic rats showed a significant cognitive dysfunction in passive avoidance and Y maze tests that was significantly attenuated following carnosine treatment. In addition, carnosine showed a hypoglycemic effect. Conclusion: This study demonstrated that treatment with carnosine for 8 weeks could improve cognitive functions in diabetic condition and part of its beneficial effect is due to its reduction of blood glucose.