Spaced taste avoidance conditioning in Lymnaea

• 15 Repeated paired presentations of sucrose and high voltage resulted in STM and LTM.
• 8 Repeated paired presentations of CS–US with interposing 3 h interval resulted in STM and LTM.
• Memory consolidated was enhanced with activation of PKC.

We succeeded in taste avoidance conditioning with sucrose as the conditional stimulus (CS) and an electrical stimulus (∼1000 V, 80 μA) as the unconditional stimulus (US). With 15 paired CS–US presentations on a single day, we were able to elicit both short-term memory (STM) and long-term memory (LTM) persisting for at least one week. However, while STM was elicited with 5, 8, 10, and 20 paired presentations of the CS–US on a single day, LTM was not. We found, however, that if we inserted a 3 h interval between a first and a second set of CS–US pairings that both 8 and 20 paired CS–US presentations on a single day was now sufficient to cause LTM formation. Exposing snails to bryostatin before or during training enhanced LTM formation such that 8 paired presentations of the CS–US resulted in LTM.