Activation of metabotropic glutamate receptor type 2/3 supports the involvement of the hippocampal mossy fiber pathway on contextual fear memory consolidation.

Elucidating the functional properties of the dentate gyrus (DG), CA3, and CA1 areas is critical for understanding the role of the dorsal hippocampus in contextual fear memory processing. In order to specifically disrupt various hippocampal inputs, we used region-specific infusions of DCG-IV, the metabotropic glutamate receptor agonist, which selectively disrupts entorhinal outputs as well as mossy fiber transmission in the hippocampus. The consequences of these injections were studied using a contextual fear conditioning (CFC) paradigm. Selective contextual memory impairment was observed in DG- and CA3-, but not in CA1-treated mice. Our results emphasize the major role played by the DG and CA3 areas in the early phases of contextual memory processing, particularly during the acquisition and early consolidation phases of CFC.