The effect of thymoquinone on short-term spatial memory, passive avoidance learning and memory of diabetic rats and the involvement of hippocampal oxidative stress

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.