Oxytocin is a neurohypophyseal peptide best known for its role as a neurohormone involved in parturition and lactation. In addition to these well established peripheral effects, there is a compelling body of converging evidence indicating that oxytocin plays a critical role in the regulation of a number of diverse centrally-mediated behavioral and cognitive processes that are highly relevant to mood regulation and mood disorders, including social attachment (Argiolas and Gessa 1990; McCarthy and Aaltemus 1997).