Capeserod is benzodioxanoxadiazolone derivative patented by patented by pharmaceutical company Synthelabo S. A. as a novel 5-hydroxytryptamine4 receptor partial agonist with potent cognition-enhancing properties. In cells expressing the 5-HT4(b) and 5-HT4(e) splice variants, Capeserod acted as a partial agonist, stimulating cAMP prodn. with a maximal effect of 40 to 50% of serotonin. However, in the rat esophagus preparation, Capeserod acted as a 5-HT4 antagonist with a pKb of 8.81. In addition, Capeserod potently improved performance in several tests of learning and memory. In the object recognition task, it improved retention at 24 h when administered i.p. or p.o. (0.001-0.1 mg/kg). This effect was antagonized by the 5-HT4 antagonist SDZ 205,557, itself without effect, demonstrating that the promnesic effects of Capeserod are mediated by 5-HT4 agonism. Capeserod also reversed the cognitive deficits of aged rats in the linear maze task and the scopolamine-induced deficit of mice in the water maze task. Furthermore, the combined administration of an inactive dose of Capeserod with the cholinesterase inhibitor rivastigmine resulted in a significant promnesic effect, suggesting a synergistic interaction. Capeserod was devoid of unwanted cardiovascular, gastrointestinal, or central nervous system effects with doses up to more than 100-fold higher than those active in the cognitive tests. These results characterize Capeserod as a novel promnesic agent acting via 5-HT4 receptors, with an excellent preclinical profile.