Abstract: We undertook this study in order to investigate the effect of dietary supplementation of walnut (Juglans regia) kernel on learning and memory capacity in a mouse model of memory impairment induced by scopolamine (SCOP). The experimental mice were fed a diet containing 9% ( high-dose treatment and prevention groups) or 6% walnut kernel (low-dose and low-dose prevention groups) while those in the other groups (control, model and positive control) were fed a normal diet. After 8 weeks of feeding, the Morris water maze (MWM) was used to evaluate the learning and memory capacity of mice. Meanwhile, brain tissues were harvested to measure the levels of malondialdehyde (MDA) and glutathione (GSH), and the activities of total superoxide dismutase (T-SOD) and acetylcholinesterase (AChE). Results showed that in the MWM trial, the escape latency of the mice in the high-dose prevention group was significantly shortened on the fourth day (P < 0.01) while the number of punctures increased (P < 0.05) and the time spent and percentage distance traveled in the target quadrant were increased (P < 0.05) when compared with the model group. Besides, AChE activity and MDA content were decreased to (0.94 ± 0.08) U/mg and (11.64 ± 0.58) nmol/mg, respectively (P < 0.05); in contrast, GSH content and T-SOD activity were increased (69.53 ± 2.11) mg/g and (93.36 ± 4.94) U/mg, respectively (P < 0.05) in brain tissue. These findings suggest that dietary supplementation of walnut kernel could inhibit oxidative damage in the brain mice, enhance cholinergic function, prevent SCOP-induced memory impairment and improve learning and memory capacity.

Key words: walnut kernel, mouse model of memory impairment, Morris water maze, antioxidant effect, learning and memory