[Pharmacological studies on Y-8894. (V) Effect on learning and memory in intact and experimentally amnesic rats]

The effects of Y-8894 on learning and memory were studied using the pole climbing avoidance (PCA) response in intact and experimentally induced amnesic rats. The following results were obtained: A single administration of Y-8894 (2.5 mg/kg, i.p.) to experimentally induced amnesic rats significantly antagonized the decrease in the mean number of PCA responses induced by an electroconvulsive shock (ECS). At a higher dose (10 mg/kg, i.p.), however, this effect was reduced. Repeated administration of Y-8894 (5 mg/kg, i.p.) significantly antagonized the facilitation of the extinction of the PCA response induced by exposure to CO2. Repeated administration of Y-8894 (2.5 mg/kg, i.p.) significantly facilitated the learning of the PCA response in intact rats. At a higher dose (5 mg/kg, i.p.), however, this effect was reduced. A single administration of Y-8894 (5 mg/kg, i.p. and 25 mg/kg, p.o.) significantly delayed the extinction of the PCA response in intact rats. These results suggest that Y-8894 has an ameliorative and facilitative effect on learning and memory in experimentally induced amnesic and intact rats.