Role of modulatory mediator serotonin in induction of epigenetic processes during long-term memory formation in Helix

Abstract

Epigenetic mechanisms of the long-term memory formation are a promising field in neurobiology. They include the posttranslational histone modifications, which leads to the chromatin remodeling and thereby influences the gene expression involved in learning. Mollusks are a popular model in neurobiology because they have a relatively simple CNS with giant neurons. We have previously found the strong induction of histone H3 acetylation and methylation during food aversion conditioning in Helix. We think that these processes are regulated by a modulatory mediator, serotonin, which plays an important role in avoidance behavior. To elucidate the influence of serotonin on the induction of epigenetic processes, we investigated the action of a nonselective antagonist of serotonin receptors, methiothepin, on acetylation and methylation of histone H3 during Helix training. We found that the treatment with methiothepin prevented the increase in methylation and acetylation of H3 in a snail’s CNS induced by training and impairs the long-term memory formation. The long-term memory formation in methiothepin-treated animals can be reversed by the treatment with histone deacetylase inhibitor, NaB. Our data confirm the important role of serotonin in the induction of the epigenetic processes during aversion conditioning in Helix.