Oxytocin (Syntocinon) is a mammalian neuropituitary hormone, a pleiotropic hypothalamic peptide and ligand for the oxytocin receptor, which contributes to labor, lactation, and pro-social behavior. Oxytocin has the ability to stimulate mammary secretion of breast milk, promote contraction of uterine smooth muscle during labor, and facilitate mothering.

Pro8-Oxytocin, a modified oxytocin (OXT) ligand, elicits more potent and efficacious responses at primate OXTR and induces stronger behavioral effects compared to the standard mammalian OXT ligand (Leu8-Oxytocin). It demonstrates lower efficacy than Vasopressin (AVP) at human AVPR1a, yet shows a higher efficacious response at marmoset AVPR1a [1].

Pro8-Oxytocin TFA, a modified oxytocin (OXT) ligand, exhibits greater potency and efficacy than the standard mammalian OXT ligand, Leu8-Oxytocin, at primate OXTR and elicits more pronounced behavioral effects. Compared to vasopressin (AVP), Pro8-Oxytocin TFA has a lower efficacious response at human AVPR1a, yet shows a higher efficacy at the marmoset AVPR1a [1].

Atosiban acetate (RW22164) is an inhibitor of the hormones oxytocin and vasopressin. It is used as an intravenous medication as a labour repressant (tocolytic) to halt premature labor. Atosiban acetate (RW22164) inhibits the oxytocin-mediated release of inositol trisphosphate from the myometrial cell membrane. As a result, there is reduced release of intracellular, stored calcium from the sarcoplasmic reticulum of myometrial cells, and reduced influx of Ca2+ from the extracellular space through voltage gated channels. In addition, Atosiban acetate (RW22164) suppresses oxytocin-mediated release of PGE and PGF from the decidua. In human pre-term labor, atosiban, at the recommended dosage, antagonizes uterine contractions and induces uterine quiescence. The onset of uterus relaxation following atosiban is rapid, uterine contractions being significantly reduced within 10 minutes to achieve stable uterine quiescence.