Treatment of Lrfn3−/− mice with fluoxetine, a medication used to treat excessive fear memory in humans such as posttraumatic stress disorders (PTSDs), which directly inhibit GluN2B-containing NMDARs (GluN2B-NMDARs), improved NMDAR-mediated currents and fear memory consolidation in Lrfn3−/− mice. Here, LRFN3 is linked to post-traumatic stress disorder.