Intracerebroventricular Microinjection of Kaempferol on Memory Retention of Passive Avoidance Learning in Rats: Involvement of Cholinergic Mechanism(s)

Kaempferol (KM) is a flavonoid found in plant-derived foods and medicinal plants. Recently, it is well established that KM plays a protective role to develop Alzheimer's disease. The current study aimed at evaluating the effect of intracerebroventricular micro-injection of KM on memory retention of passive avoidance learning (MRPAM) and identifying the potentially related cholinergic mechanisms (ChMs) in rats. In the current study, male Wistar rats randomly divided into control, vehicle and KM (10, 20 and 40 μg/rat) groups. Moreover, MRPAM was evaluated by shuttle box test. The role of ChM was studied using non-selective and selective acetylcholine antagonists (scopolamine [SCN], 4-DAMP and methoctramine [MN], respectively) as well as pirenzepine (PZ) in combination with KM. The employment of KM (40 μg/rat) improved the SCN-induced memory impairment in MRPAM. Co-treatment with KM (40 μg/rat) plus 4-DAMP significantly increased the step-through latency (STL,  < 0.05; 167 ± 28 s) and decreased the total dark chamber (TDC,  < 0.05; 121 ± 31 s) compared with those of the 4-DAMP group (STL: 75 ± 13 s; TDC: 178 ± 46 s). Co-treatment with KM (40 μg/rat) plus PZ attenuated STL, and also increased TDC ( < 0.01; 220 ± 28 s) compared with those of the PZ group. Co-treatment with KM (10 and 20 μg/rat) and MN increased STL ( < 0.05), and deceased TDC compared with those of the MN group ( < 0.01). Totally, the results of the present study showed that cholinergic system may be involved in improving effect of KM on SCN-induced memory impairment.