[Pharmacological studies on Y-8894. (VIII). Effects on learning and memory in the radial maze task in mice].

Effects of Y-8894 on learning and memory were studied using a radial maze task in intact and scopolamine-induced amnesic mice. The following results were obtained: 1) Repeated administration of Y-8894 (1, 2.5 and 5 mg/kg, i.p.) significantly increased the number of initial correct responses (ICR) in the training session in intact mice, facilitating the learning of the maze task. Dihydroergotoxine (5 mg/kg, i.p.) significantly facilitated the learning of this task in the initial stage of the training session, but non-specifically inhibited the performance in the late stage of training. Ca-hopantenate did not modify the learning of this task. 2) A single administration of Y-8894 (2.5 or 5 mg/kg, i.p.) showed an antagonistic effect on scopolamine (1 mg/kg, s.c.)-induced amnesic mice. Dihydroergotoxine (5 mg/kg, i.p.) and Ca-hopantenate (500 mg/kg, i.p.) also significantly antagonized the ICR-decreasing effect of scopolamine. These results suggest that Y-8894 has an ameliorative and/or facilitative effect on learning and memory in the radial maze task, and Y-8894 is more potent than dihydroergotoxine and Ca-hopantenate.