Layer IV-Va neurons of the granular retrosplenial cortex (A29) project and control the activity of layers II-IV neurons of dysgranular retrosplenial cortex (A30) during contextual fear memory processing

SIGWALD ERIC LUCA; PONCE NICOLAS; BIGNANTE ANALIA; DE OLMOS SOLEDAD

Mar del Plata

Congreso; XXXII Congreso Annual de de la Sociedad Argentina de Investigación en Neurociencia.; 2017

Sociedad Argentina de Investigacion en Neurociencia

Retrosplenial cortex (RSC) is connected with the hippocampal formation and neocortical areas, and has a role in cognition and spatial navigation. It is subdivided in two main regions, A29 and A30, according to their cytoarchitectural organization and connections. It is unknown how these subdivisions are functionally integrated. MK801-treatment was used asa non-invasive method for selective elimination of layers IV-Va neurons of A29 (A29MK801). Immunolabeling of GABA-associated proteins parvalbumin and calretinin revealed that MK801-treatment does not affect these neuronal populations in A29. This suggest that A29MK801 are not GABAergic neurons. Microinjections of the retrograde tracer Fluoro-Gold (FG) in superficial layers of A30 showed FG positive neurons (FG+) exclusively in layers IV-Vaof A29 distributed similarly to A29MK801 neurons. MK801 treatment dramatically reduced the number of FG+ in layers IV-Va of A29. These data indicate that A29MK801 neurons establish efferent projection to layers I-IV of A30. cFos and EGR-1 expression during contextual fear memory (CFM) encoding and retrieval indicate A29 and A30 involvement during memory processing with a different activation pattern. Ablation of A29MK801 neurons after consolidation of CFM reduces freezing and IEGs expression in A30, without affecting A29 and other related areas. Together, our results indicate A29MK801 neurons involvement in fear memory processing and their relevance in the interaction between A29 and A30.