Involvement of serotonin receptors in destabilization and re-stabilization of retrieved context and food-aversion memory in terrestrial snail Helix lucorum

The necessity for serotonin participation in memory reconsolidation in snails was demonstrated previously. So far, no research has addressed the involvement of serotonin receptors in retrieval-induced destabilization and re-stabilization of long-term context and cued memories in snails. The current study aimed to improve understanding of serotonin receptors involvement in those processes. We used a nonselective inhibitor of serotonin receptors methiothepin, and demonstrated that immediate post-reactivation methiothepin treatment induced an irreversible memory impairment, while the pre-reactivation methiothepin administration, and delayed post-reactivation methiothepin administration caused only partial memory attenuation, and memory still was well preserved. We also found that pre-reactivation methiothepin administration completely prevented the impairing effects of post-reactivation anisomycin (inhibitor of protein synthesis) injections for context and cued memories, what suggests that the pre-reactivation administration of the serotonin receptors inhibitor interfered with the retrieval-memory reactivation process. Delayed post-reactivation methiothepin administration did not prevented a significant memory impairment by anisomycin, suggesting absence of delayed effects. The results suggest that the serotonin receptors are probably involved in the process of destabilization and early phase of re-stabilization of context and food-aversion long-term memories, while less required for late phase of re-stabilization. The results obtained confirm the involvement of serotonin activity in memory reconsolidation process in mollusks.