CCKBR and major depressive disorder: Injection of CCK-B into the mouse medial prefrontal cortex induces anxiety- and depression-like behavior, decreasing time spent in the open arms of an elevated plus-maze and inducing social avoidance in a social interaction test, while blockade of the CCK-B receptor in this same brain region induces a resilient phenotype in mice subjected to chronic social defeat stress (Vialou et al., 2014).