Dimebon enhances hippocampus-dependent learning in both appetitive and inhibitory memory tasks in mice

Dimebon, a compound recently proposed for a treatment of Alzheimer’s disorder was suggested to have memory enhancing properties in pre-clinical and clinical studies. We investigated whether dimebon at doses acutely (0.1 mg/kg and 0.5 mg/kg) or repeatedly (0.1 mg/kg) administered to mice via i.p. injections, increases memory scores respectively in an appetitive and an inhibitory learning task. Acute treatment with dimebon at the dose 0.1 mg/kg did not affect learning scores in either 3-month-old C57BL/6N or CD1 mice. Acute treatment with higher dose of dimebon (0.5mg/kg) was found to enhance inhibitory learning in 3- and 7-month-old mice as shown in the step-down avoidance paradigm in C57BL/6N mice. No effects on learning were seen in CD1 mice. In a model of appetitive learning, a spatial version of the Y-maze, repeated treatment with dimebon increased the rate of correct choices and decreased the latency of accessing a water reward after water deprivation. Repeated administration of dimebon also increased the duration of drinking behaviour during training/testing procedures although behaviours in others tests or water consumption were not altered. Acute treatment of water-deprived and non-water-deprived mice with dimebon also did not affect their water intake. Our data suggest that dimebon enhances hippocampus-dependent learning in both appetitive and inhibitory tasks in mice.