EFFECTS OF ENVIRONMENTAL ENRICHMENT ON MOSSY FIBERS AND THEIR RELATIONSHIP WITH MICROGLIA

The hippocampus is one of the most plastic regions of the central nervous system due to the constant remodeling of synaptic contacts and because neurogenesis continues throughout adult life. Newly generated granular cells incorporate into the hippocampal circuitry and extend their axons, known as mossy fibers, establishing new contacts with CA3 pyramidal cells. Lifestyle, and in particular environmental enrichment, modulates brain function by promoting neuro- and synaptogenesis in the hippocampus. Furthermore, microglia have been proposed as a modulator of the environmental effects on adult neurogenesis. In this project, we optimized a protocol for the analysis of new mossy fibers and their glutamatergic terminals in CA3 by using the specific markers PSA-NCAM and vGlut1, respectively. We also analyzed the relationship between the axonal fibers and terminals with microglia. The application of this protocol allowed us to detect differences between CA3 regions and the increase of excitatory terminals of the new mossy fibers after environmental enrichment. Additionally, we observed an increase in hippocampal volume and in the number of microglia cells in the whole CA3 region of the hippocampus of enriched animals.
Funding: Science and Innovation Spanish Ministry: PID2022-140525NB-I00 and PID2022-140456NB-I00. POCTEP: Cross-3DTool-4ALS (Programa Interreg VI-AEspaña-Portugal (POCTEP) 2021-2027), and Erasmus+ programme Partnership for Cooperation (2023-1-PL01-KA220-HED-000160284).