In placental mammals, the paralogous nonapeptides oxytocin (OXT:Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly) and arginine vasopressin (AVP:Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly) play an important role in physiological andbehavioral functions, such as water homeostasis, vasoconstriction, lactation,uterine contractions, parental care, control of aggression, anxiety and stress(Gimpl and Fahrenholz, 2001; Cagliani et al., 2009; Young and Flanagan-Cato, 2012; McCall and Singer, 2012). This evidence concerns the gene OXT and Anxiety.