EFFECT OF THE SEROTONERGIC SYSTEM ON CONSOLIDATION AND RECONSOLIDATION OF MEMORY IN AN INVERTEBRATE

SILVIA PEDETTA AND HÉCTOR MALDONADO

Lucca, Italia

Congreso; Gordon Research Conference - Genes and Behavior; 2008

Serotonin is a biogenic amine widely distributed in both vertebrates and invertebrates. It is involved in a variety of physiological processes, as cognition and aggression. In decapod crustaceans it is considered to be related to the dominant status. We have studied the aggressive behaviour in the crab Chasmagnathus and its relation with memory ability for a paradigm of contextual fear, termed context-signal memory (CSM). Dominant crabs showed a poorer retention in the CSM; but only if memory was evaluated after the encounters. Therefore, it is understood as a consequence of the previous fight, and suggests that the mechanisms involved in the building up of the agonistic condition might mediate cognitive processes. Considering the role assigned to serotonin in aggression, we propose that this amine may be related to the impairment of memory in dominants. For this purpose, we started the relationship between the serotonergic system and memory. Our first objective was to characterize the effect of serotonin administration on the CSM. We found that serotonin has a dose-dependent amnesic effect on consolidation. A dose of 10-3 M has a strong effect, while the dose of 10-5 M ineffectual. The higher dose was effective when given until 3 h after training. During reconsolidation, serotonin administration is also amnesic until 3 h after the reminder. Finally, we studied the effect of endogenous serotonin on CSM. Fluoxetine, a reuptake inhibitor, also impairs memory consolidation. This result suggests that serotonin is playing a role in the codification of training information. Taken together, the results provide the first evidences of the action of serotonin on an associative learning in crustaceans and allow us to speculate it could be responsible of the worse memory ability expressed by dominants in the CSM paradigm. Given that serotonin seems to modulate fear processes, we propose that it might exert its action by weakening the negative significance of the training experience.