Wnt proteins activate different signaling pathways, such as the canonical Wnt/β-catenin signaling pathway and non-canonical β-catenin-independent signaling pathway and have been related to several functions in central nervous system, including learning and memory. However, whether these signaling pathways are required in the medial prefrontal cortex (mPFC) for fear memory acquisition, consolidation and retrieval remains unclear. To address this question, we submitted male rats to a contextual fear conditioning (CFC) paradigm, and administered canonical Wnt/β-catenin and non-canonical Wnt/Ca2+ signaling pathways inhibitors, DKK1 and SFRP1, respectively, into the prelimbic (PrL) subdivision of the mPFC at different moments and evaluated short-term and long-term memory acquisition, consolidation and retrieval. We found that blocking canonical Wnt/β-catenin and non-canonical Wnt/Ca2+ signaling pathways 15 min before or immediately after CFC training had no effect on STM and LTM of CFC, while their blockade 15 min before the retention test prevented the retrieval of STM and LTM of CFC. These results highlight the importance of the mPFC in fear memory retrieval demonstrating that both canonical Wnt/β-catenin and non-canonical Wnt/Ca2+ signaling pathways participate in this process. To understand how brain systems act on fear memories could provide a new target for the treatment of fear related disorders such as post-traumatic stress disorder and other anxiety disorders.
Keywords: Canonical Wnt/β-catenin signaling; Fear memory; Non-canonical Wnt/Ca(2+)signaling; Prefrontal cortex; Retrieval.
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