Effects of vinconate on scopolamine-induced memory impairment in rhesus monkeys

Effects of vinconate on specifically impaired short-term memory were studied in rhesus monkeys. Monkeys were trained to perform for orange juice reinforcement under a matching-to-sample response procedure. In the procedure, monkeys had to choose one of two stimuli that had the same color as the sample stimulus. Half of a daily session consisted of simultaneous trials where the sample stimulus was present during the time of choice. The other half of the session consisted of delayed trials where the sample stimulus had been presented but withheld at the time of choice. After the repeated training, the matching-to-sample responses were established with the percentage of correct choice responses (CR%) in both types of trials exceeding 90%. The doses of scopolamine, intervals between administration of this drug and the start of test session, and delay times in delayed trials were adjusted from one monkey to another so that delayed matching-to-sample responses were impaired by scopolamine while simultaneous matching-to-sample responses were less impaired by this drug. Scopolamine (32 or 45 micrograms/kg, s.c.) decreased the CR% for delayed trials more markedly than the CR% for simultaneous trials in four monkeys. Intragastrically administered vinconate at 16 mg/kg attenuated the scopolamine-induced short-term memory impairment. These results suggested that vinconate possesses specific ameliorating action on memory impairment caused by hypofunction of the cholinergic system in the brain.