Importantly, global 5-HT1A knockout (Santarelli et al., 2003) or specific deletion of the gene in hippocampal dentate gyrus granule cells (Samuels et al., 2015) prevents fluoxetine-induced hippocampal neurogenesis and anti depressant and anti-anxiety actions, implicating hippocampal 5-HT1A receptors in fluoxetine action (Figure 2). The gene discussed is HTR1A; the disease is Anxiety.