ABSTRACT
Chronic diabetes mellitus accompanies disturbance in learning, memory, and cognitive skills. With regard to anti-diabetic and antioxidant activity of thymoquinone [TQ], the effect of its chronic administration on learning and memory of diabetic rats was investigated. In this experimental study, male rats were divided into control, high dose TQ-treated control, diabetic, and low and high dose TQ- treated diabetic groups. TQ was administered i.p. at doses of 2.5 and 5 mg/kg one week after diabetes induction by streptozotocin, for 5 weeks. For evaluation of learning and memory, initial [IL] and step-through latencies [STL] were determined at the end of the study using passive avoidance test, and alternation behavior percentage was obtained using Y maze. In addition, hippocampal homogenate malondialdehyde [MDA] level was measured. STL significantly decreased in diabetic [p<0.01] and TQ-treated diabetic groups [p<0.001]; TQ treatment did not improve it in any of its doses. Alternation percentage was significantly lower in the diabetic group compared to the control [p<0.005]. TQ-treated diabetic group [at a dose of 5 mg/kg] showed a significantly higher score compared with diabetic group [p<0.01]. Diabetic rats also showed a significant increase in tissue level of malondialdehyde [p<0.01] and TQ treatment significantly reduced the level of MDA [p<0.05]. Although chronic treatment of diabetic rats with TQ could not enhance the capability of consolidation and recall in diabetic rats, it could improve spatial memory in them; part of its effect is via attenuation of lipid peroxidation