Effects of the nitric oxide donor molsidomine on different memory components as assessed in the object-recognition task in the rat

Rationale: Nitric oxide (NO) is sought to be a novel intracellular messenger in the central nervous system. Recently, NO involvement in learning and memory processes has been proposed. Compounds that inhibit NO synthase, the key synthesizing enzyme, may block cognition, while NO donors may facilitate it. Objectives: The present study was designed to further investigate in the rat the effects on distinct memory processes exerted by the NO donor molsidomine. For this aim, the object-recognition task was chosen. This test is based on the differential exploration of a new and familiar object. Methods: Object recognition was evaluated in a two-trial nonrewarded paradigm. In a first study, the influence of the retention time (the delay between the two trials) on the performance of 3-month-old male rats was assessed. Subsequently, the effects of molsidomine (2 mg/kg and 4 mg/kg), injected i.p., on acquisition, storage, and retrieval of information were evaluated. For the latter experiments, the delay condition at which recognition memory was extinguished in the normal rat was used (24 h). Results: Under our experimental conditions, object recognition was extinguished in the rat when an intertrial interval (ITI) of 24 h was utilized. Using this ITI, molsidomine at 4 mg/kg but not at 2 mg/kg improved the animal's performance in the object-recognition task, suggesting that molsidomine affected acquisition, storage, and retrieval of information. Conclusions: These results indicate that the NO donor molsidomine may modulate different aspects of memory.