One of ways of nitric oxide (NO) influence on neuronal activity is S-nitrosylation, the covalent attachment of NO group to the thiol side chain of cysteine, changes function of existing proteins, inhibiting their normal role in physiological functions including memory. Influence of NO via GC activates intracellular signaling cascades and triggers increased synthesis ofproteins, influencing the memory. In the present paper we want to express and test the hypothesis that the NO is necessary both for erasure and development of memory. In our experiments in terrestrial snail Helix we tested the idea that NO besides well shown participation in memory development is involved in erasure/lockout of memory during relearning and reconsolidation.