Reminder effects - reconsolidation or retrieval deficit? Pharmacological dissection with protein synthesis inhibitors following reminder for a passive-avoidance task in young chicks.

It is generally accepted that memory formation involves an irreversible passage via labile phases to the stable form of 'long-term memory' impervious to amnestic agents such as protein synthesis inhibitors. However, recent experiments demonstrate that reactivation of memory by way of a reminder renders it labile to such inhibitors, suggesting that such retrieval is followed by a so-called reconsolidation process similar or identical in its cellular and molecular correlates to that occurring during the initial consolidation. We compared the effects of the protein synthesis inhibitor anisomycin and the glycoprotein synthesis inhibitor 2-deoxygalactose on the temporal dynamics and pharmacological sensitivity of initial consolidation and memory expression following a reminder in a one-trial passive-avoidance task in day-old chicks. This comparison revealed three differences between the action of the inhibitors on newly formed compared with reactivated memory. First, the recall deficit after the reminder was temporary, whilst the amnesia following inhibitor treatment during training was stable. Second, the sensitive period for the effect of anisomycin was shorter in the reminder than in the training situation. Third, the effective dose for either inhibitor for reminder-associated amnesia was several times lower than for amnesia developing after training. Thus though like initial consolidation, memory expression at delayed periods following reminder depends on protein and glycoprotein synthesis, the differences between the temporal and pharmacological dynamics in the two situations point to the distinct character of the molecular processes involved in postreminder effects.