Synergistic effects of antidementia drugs on spatial learning and recall in the APP23 transgenic mouse model of Alzheimer's disease.

Current treatment of Alzheimer's disease rests on cholinergic and anti-glutamatergic substances. It has been suggested that acetylcholine is required for memory acquisition but is less important for memory retrieval. It was our goal to investigate the effects of treatment with donepezil, memantine, and a combination thereof on spatial memory. We assessed spatial memory of male wild type and B6C3-Tg(APPswe,PSEN1dE9)85Dbo (APP23) transgenic animals in a complex dry-land maze. Animals were treated with donepezil (1 mg/kg) and memantine (10 mg/kg). Total time to escape from the maze decreased in 4.5 month old sham-treated wild-type animals and, to a lesser extent, in APP23 animals. Analysis of time spent moving and resting revealed that the treatment effect is conferred by a reduction of the moving time for donepezil and a reduction of the resting time for memantine. Combination treatment with donepezil and memantine fostered a greater improvement than treatment with either substance alone. We conclude that enhancement of spatial learning in a dry-land maze on cholinergic or anti-glutamatergic treatment is differentially conferred during moving of the animals, possibly reflecting acquisition of spatial information, and resting of the animals, possibly reflecting retrieval of spatial information. Combination treatment with donepezil and memantine exerts a synergistic effect improving both moving time and resting time and thus possibly both spatial learning and retrieval.