Effects of the nitric oxide synthase inhibitor L-NAME on different memory components as assessed in the object recognition task in the rat.

Nitric oxide (NO) is sought to be an intracellular messenger in the central nervous system and its implication in learning and memory is well documented. Compounds that inhibit nitric oxide synthase (NOS), the key synthesizing enzyme, block cognition, though discrepant findings, in this context, have also been reported. The present study was designed to investigate in the rat: (a) the effects on recognition memory exerted by low doses of the NOS inhibitor L-NAME and (b) the ability of this compound in modulating different mnemonic processes (acquisition, storage and retrieval). For this aim, the object recognition task was selected. In a first study, pre- or post-training systemic administration of L-NAME (1, 3 and 10mg/kg, i.p.) did not disrupt animals' performance in this recognition memory paradigm. Subsequently, L-NAME (1 and 3, but not 10mg/kg, i.p.) antagonized delay-dependent deficits in the object recognition task suggesting that L-NAME affected acquisition, storage and retrieval of information. These results indicate that the NOS inhibitor L-NAME may modulate different aspects of memory.