AMPA receptor trafficking in recent vs. remote memory

It is now established that iteration of memory circuits takes place from hippocampus to cortical regions. The recall of recent event is largely dependent on the hippocampus networks, however, with passage of time, the cortical regions become largely involved in the recall of remote events. Molecular events, specifically, the AMPA receptor regulation underlying this iteration remains largely elusive. Method: Separate groups of mice were fear conditioned using contextual fear conditioning paradigm. Memory retrieval test was performed 1 day post training, for the recent memory group, together with respective controls. Where as, in case of remote group retrieval was performed 30 days post training. One hour post retrieval session, hippocampus and anterior cingulate regions were harvested after decapitation from all the groups, which were processed for synaptic membrane isolation and quantitative western blotting. Results: We observed endocytosis of GluAl and 2 exclusively in the anterior cingulate regions in the remote memory group, one hour post retrieval session, whereas in recent group, endocytosis of AMPA receptor units was only observed in the hippocampal regions. The endocytosis of GluAl-2 containing AMPARs upon retrieval, showed the weakened state of synapse. At this time point modification in content and strength of memory is possible for treatment of traumatic memories. (C) 2016 Elsevier B.V. All rights reserved.