Persistence of spatial memory induced by spaced training involves a behavioral-tagging process

Arc and BDNF mediated effects of hippocampal astrocytic glutamate uptake blockade on spatial memory stages

Glutamate is involved in fundamental functions, including neuronal plasticity and memory. Astrocytes are integral elements involved in synaptic function, and the GLT-1 transporter possesses a critical role in glutamate uptake. Here, we study the role of GLT-1, specifically located in astrocytes, in the consolidation, expression, reconsolidation and persistence of spatial object recognition memory in rats. Administration of dihydrokainic acid (DHK), a selective GLT-1 inhibitor, into the dorsal hippocampus around a weak training which only induces short-term memory, promotes long-term memory formation. This promotion is prevented by hippocampal administration of protein-synthesis translation inhibitor, blockade of Activity-regulated cytoskeleton-associated protein (Arc) translation or Brain-Derived Neurotrophic Factor (BDNF) action, which are plasticity related proteins necessary for memory consolidation. However, DHK around a strong training, which induces long-term memory, does not affect memory consolidation. Administration of DHK before the test session impairs the expression of long-term memory, and this effect is dependent of Arc translation. Furthermore, DHK impairs reconsolidation if applied before a reactivation session, and this effect is independent of Arc translation. These findings reveal specific consequences on spatial memory stages developed under hippocampal GLT-1 blockade, shedding light on the intricate molecular mechanisms, governed in part for the action of glia.

Exploring gene-drug interactions for personalized treatment of post-traumatic stress disorder

Introduction

Post-Traumatic Stress Disorder (PTSD) is a mental disorder that can develop after experiencing traumatic events. The aim of this work is to explore the role of genes and genetic variations in the development and progression of PTSD.

Methods

Through three methodological approaches, 122 genes and 184 Single Nucleotide Polymorphisms (SNPs) associated with PTSD were compiled into a single gene repository for PTSD. Using PharmGKB and DrugTargetor, 323 drug candidates were identified to target these 122 genes. The top 17 drug candidates were selected based on the statistical significance of the genetic associations, and their promiscuity (number of associated genestargets) and were further assessed for their suitability in terms of bioavailability and drug-like characteristics. Through functional analysis, insights were gained into the biological processes, cellular components, and molecular functions involved in PTSD. This formed the foundation for the next aspect of this study which was to propose an efficient treatment for PTSD by exploring drug repurposing methods.

Results

The main aim was to identify the drugs with the most favorable profile that can be used as a pharmacological approach for PTSD treatment. More in particular, according to the genetic variations present in each individual, the relevant biological pathway can be identified, and the drug candidate proposed will specifically target said pathway, accounting for the personalized aspect of this work. The results showed that the drugs used as off-label treatment for PTSD have favorable pharmacokinetic profiles and the potential drug candidates that arose from DrugTargetor were not very promising. Clozapine showed a promising pharmacokinetic profile and has been linked with decreased psychiatric symptoms. Ambrucin also showed a promising pharmacokinetic profile but has been mostly linked with cancer treatment.

Modulation of memory reconsolidation by adjacent novel tasks: timing defines the nature of change

Reconsolidation turns memories into a responsive state that allows their modulation until they stabilize again. This phenomenon attracted remarkable attention due to its potential impact on therapeutics and education. Recent evidence revealed that different memories undergo reconsolidation via a behavioral tagging process. Thus, their re-stabilization involves setting "reconsolidation-tags" and synthesizing plasticity-related proteins for their capture at the tagged sites. Here, we studied the possibility of affecting these fundamental mechanisms to modulate reconsolidation. Our findings, in laboratory rats, indicate that exploring a novel environment 60 min before or after memory reactivation improves spatial object recognition memory by promoting protein synthesis. Conversely, experiencing novelty immediately after reactivation impairs the reconsolidation by affecting the tags. Similar effects, but with a different optimal time window for improvement, occur in inhibitory avoidance memory. These results highlight the possibility of modulating existing memories using non-invasive interventions that selectively affect the fundamental mechanisms of behavioral tagging during their reconsolidation.

A behavioral tagging account of kinase contribution to memory formation after spaced aversive training

Long-term memory (LTM) can be induced by repeated spaced training trials. Using the weak inhibitory avoidance (wIA) task, we showed that one wIA session does not lead to a 24-h LTM, whereas two identical wIA sessions spaced by 15 min to 6 h induce a 24-h LTM. This LTM promotion depends both on hippocampal protein synthesis and the activity of several kinases. In agreement with the behavioral tagging (BT) hypothesis, our results suggest that the two training sessions induce transient learning tags and lead, via a cooperative effect, to the synthesis of plasticity-related proteins (PRPs) that become available and captured by the tag from the second session. Although ERKs1/2 are needed for PRPs synthesis and CaMKs are required for tag setting, PKA participates in both processes. We conclude that the BT mechanism accounts for the molecular constraints underlying the classic effect of spaced learning on LTM formation.