Herbal Extracts Combination (WNK) Prevents Decline in Spatial Learning and Memory in APP/PS1 Mice through Improvement of Hippocampal Aβ Plaque Formation, Histopathology, and Ultrastructure

To investigate the cognitive enhancement effect of WNK, an extracts combination of P. ginseng,  G. biloba, and C. sativus L. and possible mechanisms, 5-month-old APP/PS1 transgenic mice were used in this study. After 3 months of administration, all mice received Morris water maze (MWM) training and a probe test. Mouse brain sections were detected by immunohistochemistry, HE staining, and transmission electron microscopy. MWM results showed significant difference between transgenic mice and nontransgenic littermates (P < 0.05, P < 0.01). WNK-treated mice exhibited enhanced maze performance over the training progression, especially better spatial memory retention in probe test compared to transgenic mice (P < 0.05, P < 0.01) and better spatial learning and memory at the fourth day of MWM test compared to EGB761- (G. biloba extract-) treated ones (P < 0.05). Hippocampal Aβ plaque burden significantly differed between APP/PS1 and littermate mice (P < 0.001), while decreased Aβ plaque appeared in WNK- or EGB761-treated transgenic brains (P < 0.05). Neurodegenerative changes were evident from light microscopic and ultrastructural observations in transgenic brains, which were improved by WNK or EGB761 treatment. These data indicate WNK can reduce the decline in spatial cognition, which might be due to its effects on reducing Aβ plaque formation and ameliorating histopathology and ultrastructure in hippocampus of APP/PS1 mouse brain.