Objective: To investigate learning-memory deficit in different ages of AD-like APP transgenic mice and to observe the protective effects of 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside (TSG), which is the main component of Polygonum multiflorum, on learning-memory abilities. Methods: PDAPPV717I transgenic (Tg) mice were randomly divided into 3 model groups (4, 10 and 16 months old mice) and TSG treated (at doses 120 and 240 mu mol/kg/d) groups. TSG was administered to some Tg mice with an age range 4-10 months. In untreated 10 months old Tg mice, the TSG was administrated to those falling in the age range 10-16 months. For the control group we adopted the same age and background C57BL/6J mice. The learning-memory ability was measured by applying Morris water maze (MWM) and object recognition test (ORT). Results: In the 4 months old PDAPPV717I Tg mice, the learning-memory deficit was detected. The escape latency in MWM was prolonged, and the discrimination index decreased in ORT. In the 10 months old Tg mice, the learning-memory deficit was aggravated. TSG improved all spatial learning-memory impairment in MWM as well as the object recognition impairment in ORT. In the 16 months old Tg mice, the learning-memory deficit remained to exist but abated a lot. TSG showed significant improvement in learning-memory ability in both MWM and ORT. Conclusion: PDAPPV717I transgenic mice with an age range 4-16 months revealed the existence of learning-memory deficit compared with the control group. Tetrahydroxystilbene glucoside not only prevents, i.e. at an early stage, the learning-memory deficit in AD-like model, but also can reverse the learning-memory deficit in the late stage of AD-like model. Thus, TSG could be considered among the future therapeutic drugs indicated for the treatment of AD. (c) 2006 Elsevier B.V. All rights reserved.