CCK and major depressive disorder: As CCK in rats is found to be more highly expressed in the posterior PVT, and stimulation of this subregion affects anxiety-like behavior (Barson et al., 2020) and the intake of drugs of abuse (Pandey et al., 2019; Matzeu and Martin-Fardon, 2020), we hypothesize that CCK in cells of the PVT could promote anxiety- and depression-like behavior and promote the intake of drugs of abuse.