Objective: To investigate the effects of timosaponins, one group of the two major components of Anemarrhean asphodeloides Bge, on the learning and memory capacities of rats with dementia induced by amyloid beta-peptide (25-35) [Abeta (25-35)].

Methods: Sixty SD rats were randomized into 6 groups (n=10) and except for those in the control group, all other rats were subjected to lateral cerebral ventriclar injection of aggregated Abeta (25-35) to prepare rat models of dementia. Twenty- four hours after the injection, the rats received intragastric administration of timosaponins at 3 different doses (treatment group) or Ginkgo biloba extract EGB761 on a daily basis for 14 consecutive days. From postoperative days 8 to 14 after Abeta (25-35) injection, Morris water maze test was performed to evaluate the effects of Abeta (25-35) and the therapeutic agents timosaponins on the learning and memory capacity of the rats. On day 14, the level of malonaldehyde (MDA), superoxide dismutase (SOD) activity and total antioxidation capacity in the brain tissue of the rats were measured.

Results: Abeta (25-35) induced significant learning and memory impairment in the rats, which had lowered SOD activity and total antioxidation capacity (P<0.01) with elevated MDA level (P<0.05). Compared with the rats in dementia model group, those receiving timosaponin treatment at different doses all manifested alleviation of learning and memory impairment (P<0.05), with enhanced SOD activity (P<0.05) and total antioxidation capacity (P<0.01) and reduced MDA level (P<0.05) in the brain tissue.

Conclusion: Timosaponins can remarkably enhance the learning and memory capacities in rats with Abeta (25-35)-induced dementia, presumably in relation to their actions to promote the scavenging of the free radicals.