from wiki:
oxytocin has the distinction of being the very first polypeptide hormone to be sequenced and synthesized biochemically by Vincent du Vigneaud et al. in 1953.
Oxytocin is best known for its roles in female reproduction: 1) it is released in large amounts after distension of the cervix and vagina during labor, and 2) after stimulation of the nipples, facilitating birth and breastfeeding, respectively. Recent studies have begun to investigate oxytocin’s role in various behaviors, including orgasm, social recognition, pair bonding, anxiety, trust, love, and maternal behaviors.
Stress causes less secretion of oxytocin and thus less trust to people and government.