ERα and ERβ knock-out (KO) mouse models as well as double knock-outs (ERαβKO) have played an important role in this research and demonstrated an implication of one or both receptors in the control of male and female sexual behavior [93]–[97], male aggressive behavior [98]–[100], social interactions and anxiety [101], [102] and in the activity of various neurochemical systems [103], [104]. This evidence concerns the gene ESR2 and Anxiety.