The researchers tested the effects of synthetic hormones on sheep's mammary glands. They found that oxytocin, arginine-vasopressin, and lysine-vasopressin injections increased intramammary pressure, with oxytocin having the strongest effect. Higher doses of hormones led to quicker pressure increases. Arginine-vasopressin had only 14.5% of the milk-ejection activity of oxytocin, while lysine-vasopressin had 10.2%.