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Object recognition memories (ORM) can incorporate new information upon reactivation. This update initially involves destabilization of the original memory, which is followed by restabilization of the upgraded engram through a reconsolidation process that requires gene expression and protein synthesis in the hippocampus. We found that when given in dorsal CA1 either immediately after training or 15 min before ORM reactivation in the presence of a novel object, the dopamine D1/D5 receptor antagonist SCH23390 did not affect ORM consolidation, expression or retention but impeded the amnesia caused by the post-retrieval administration of the mRNA synthesis inhibitor α-amanitin or the protein synthesis blocker anisomycin. This anti-amnesic effect was not observed when SCH23390 was given immediately after training and again 15 min before memory reactivation. Our results demonstrate that hippocampal D1/D5 receptors are not needed for formation, retrieval or post-retrieval restabilization of the ORM trace but are essential for its destabilization when reactivation occurs together with the incorporation of new information into the original memory. Importantly, they also suggest that reenactment of the animal's post-learning neurochemical milieu at the moment of memory reactivation can be a boundary condition for reconsolidation., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Memory is destabilized during retrieval-induced reconsolidation and can therefore be disrupted or modified. In the present study, we examined the role of translation and transcription processes in long-term food aversion memory reconsolidation in the snail Helix lucorum. The administration of the protein synthesis inhibitor anisomycin followed by a reminding procedure (presentation of the conditioned stimulus) led to the development of amnesia that persist for 2 weeks or longer. Administration of the mRNA synthesis inhibitors actinomycin D, α-amanitin, or DRB (5,6-dichloro-1-β-D-ribofuranosylbenzimidasole) followed by a reminding procedure did not affect memory retrieval. Our present findings indicate that proteins synthesized from preexisting mRNA that is transcribed during learning and stored in a silent state may be involved in the mechanisms of conditioned food aversion reconsolidation., (Copyright © 2012 Elsevier B.V. All rights reserved.)

RNA polymerase II is an essential nuclear multi subunit enzyme that transcribes nearly the whole genome. Its inhibition by the alpha-amanitin toxin leads to cell death. The enzyme of Plasmodium falciparum remains poorly characterized. Using a complementation assay in yeast as a genetic test, we demonstrate that five Plasmodium putative RNA polymerase subunits are indeed functional in vivo. The active site of this enzyme is built from the two largest subunits. Using site directed mutagenesis we were able to modify the active site of the yeast RNA polymerase II so as to introduce Plasmodium or human structural motifs. The resulting strains allow the screening of chemical libraries for potential specific inhibitors., (Copyright © 2011 Elsevier B.V. All rights reserved.)