Protective effects of myricetin on chronic stress-induced cognitive deficits

The aim of the present study is to investigate the possible effects of chronic administration of myricetin, a natural flavonoid, on chronic stress-induced learning and memory deficits in mice. The mice were restrained daily 4 h/day for 21 days in well-ventilated plexiglass tubes without access to food and water. These animals were injected with myricetin or vehicle 40 min before each restraint stress over a period of 21 days. Then, spatial learning and memory of the mice were evaluated by the Morris water maze task. We did not observe a significant difference in the escape latency in mice subjected to repeated restraint stress, which indicates that learning ability was not affected by restraint stress. However, the spatial memory ability was significantly impaired in the repeatedly restrained mice. Myricetin administration specifically increased the time spent in the target quadrant in mice exposed to chronic stress in the probe trial as tested in the Morris water maze task. Further studies showed that myricetin treatment decreased plasma adrenocorticotrophic hormone levels of those mice subjected to repeated restraint stress. The effect of myricetin on the levels of brain-derived neurotrophic factor (BDNF) in hippocampus was also investigated. The result showed that myricetin normalized the decreased BDNF levels in mice subjected to repeated restraint stress. These findings provide more evidence that chronic administration of myricetin improves spatial memory in repeatedly restrained mice and BDNF signaling in the hippocampus may be involved in the protective effects of myricetin.