Oxytocin and behavior

The rodent and human studies entail that oxytocin facilitates a range of social interactions (i.e., pro-social behaviors). These involve:

- Pair bonding—the tendency of two persons in a sexual relationship to stay altogether—in both sexes.

- Triggering (though not maintaining) maternal behavior.

- Trust between persons.

Such behaviors are considered to be mediated by projections of hypothalamic oxytocin neurons to limbic structures included in emotion, and to the ventral tegmental region (VTA) of the dopaminergic reward system.

The oxytocin neurons fire during sexual intercourse in both men and women, and oxytocin generates feelings of pleasure and raised libido. MRI of women shown photographs of their lovers (though not platonic friends) illustrates raised activity in the anterior cingulate cortex, an area reactive to oxytocin. It is postulated that oxytocin discharge becomes conditioned by repeated intercourse with similar partner and this underlies pair bonding. In this model sexual or romantic love is seen as an addiction to a particular individual organized by oxytocin. Triggering the maternal behavior in rats includes raised oxytocin signaling to the VTA and therefore raised dopamine discharge from the nucleus accumbens. The human MRI recommends that facilitation of trust by oxytocin could manage by suppressing fear circuitry of the brainstem and amygdala.

The feelings of empathy and love felt by individuals dosed with 3,4-methylenedioxy-methamphetamine could be since MDMA stimulates oxytocin secretion by the activation of 5-HT1A serotonin receptors. Acute stress reduces oxytocin discharge through actions of noradrenaline (i.e., norepinephrine) and adrenaline (that is, epinephrine). Therefore stress decreases milk let-down, prolongs labor, and has unfavorable effects on pro-social behaviors.