• Neuroscience · Aug 2022

    PKMζ maintains remote contextual fear memory by inhibiting GluA2-dependent AMPA receptor endocytosis in the prelimbic cortex.

    • Lucas A Marcondes, Jociane de C Myskiw, Eduarda G Nachtigall, Rodrigo F Narvaes, Ivan Izquierdo, and Cristiane R G Furini.
    • Laboratory of Cognition and Memory Neurobiology, Brain Institute, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga, 6690 - 3rd Floor, 90610-000 Porto Alegre, RS, Brazil; Memory Center, Brain Institute, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga, 6690 - 2nd Floor - HSL, 90610-000 Porto Alegre, RS, Brazil.
    • Neuroscience. 2022 Aug 10; 497: 97-106.

    AbstractFear memories allow animals to recognize and adequately respond to dangerous situations. The prelimbic cortex (PrL) is a crucial node in the circuitry that encodes contextual fear memory, and its activity is central for fear memory expression over time. However, while PrL has been implicated in contextual fear memory storage, the molecular mechanisms underlying its maintenance remain unclear. Protein kinase M zeta (PKMζ) is a persistently active enzyme which has been shown to maintain many forms of memories by inhibiting the endocytosis of GluA2-containing AMPA receptors. Therefore, we hypothesized that PKMζ action upon GluA2-containing AMPARs could be a mechanism for contextual fear memory maintenance in the PrL. To test this hypothesis, we trained rats in a contextual fear conditioning (CFC) paradigm and administered intra-PrL infusions of the PKMζ inhibitor ZIP, the GluA2-dependent endocytosis inhibitor GluA23Y or the inactive peptide GluA23Y(s), either two or twenty days after conditioning, and assessed long-term memory retention twenty-four hours later. We found that acute inhibition of GluA2-dependent AMPAR endocytosis in the PrL does not affect recent or remote contextual fear memory maintenance. Also, PKMζ inhibition in the PrL does not impair the maintenance of recent contextual fear memory. However, we found that inhibition of prelimbic PKMζ at a remote time point disrupts contextual fear memory maintenance, and that blocking GluA2-dependent removal of AMPARs prevents this impairment. Our results confirm the central role of PrL in fear memory and identify PKMζ-induced inhibition of GluA2-containing AMPAR endocytosis as a key mechanism governing remote contextual fear memory maintenance.Copyright © 2021 IBRO. Published by Elsevier Ltd. All rights reserved.

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