Oxytocin
It has been shown that oxytocin differentially affects males and females. Females who are administered oxytocin are overall faster in responding to socially relevant stimuli than males who received oxytocin. Additionally, after the administration of oxytocin, females show increased amygdala activity in response to threatening scenes; however, males do not show increased amygdala activation. This phenomenon can be explained by looking at the role of gonadal hormones, specifically estrogen, which modulate the enhanced threat processing seen in females. Estrogen has been shown to stimulate the release of oxytocin from the hypothalamus and promote receptor binding in the amygdala.
Romance (love)
In the search for the root of intimate partner violence, intranasal oxytocin was administered to a control group and a group of participants with aggressive tendencies. Participants were then surveyed on how willing they were to engage in 5 behaviors towards their romantic partner. What they found was that oxytocin increased IPV inclinations only among the participants with a predisposition towards aggressive tendencies. Oxytocin decreases trust and prosocial behavior in individuals with interpersonal difficulties. This, coupled with its role in relationship maintenance, illustrates that oxytocin serves to instill a sense of territoriality and protectiveness towards a mate.