The role of retinoids in memory reconsolidation and extinction following appetitive conditioning

Retinoic acid, the active metabolite of vitamin A, is an important signaling molecule during vertebrate synaptic plasticity and learning and memory. We have shown that it also plays a role in long-term memory formation following both operant and classical conditioning in the invertebrate, Lymnaea stagnalis. Following retrieval, recent long-term memories can undergo additional processing whereby they can be updated and re-stabilized during reconsolidation, or suppressed during extinction. Here, we examined whether retinoic acid is involved in post-retrieval memory processing by utilizing appetitive classical conditioning of Lymnaea. We show that exposure to retinoid signaling inhibitors differentially disrupts memory reconsolidation, depending on the need for protein synthesis and the extent of training received. We also show that memory extinction is inhibited in the presence of both retinoid inhibitors and protein synthesis inhibitors, regardless of the extent of training. These findings suggest that retinoids play a role in the continued processing of implicit memories following retrieval.