HTR1A and major depressive disorder: Such upregulation of 5-HT1A receptor signaling likely contributes to the therapeutic action of antidepressants, since a reduction of the 5-HT1A receptor levels in cortical regions has been observed in animal models of depression and anxiety disorders (Overstreet et al., 2003; Shively et al., 2006) and in patients with depression (Savitz et al., 2009; Stockmeier et al., 2009) and anxiety disorders (Neumeister et al., 2004; Sullivan et al., 2005; Lanzenberger et al., 2007).