​Each prostaglandin (PG) evokes distinct physiological effects through specific cell surface receptors. PG_I2 (prostacyclin) promotes smooth muscle relaxation and inhibits platelet activation through the IP receptor. Agonists of IP, including epoprostenol, iloprost, and treprostinil, are effective in relaxing pulmonary arterial smooth muscle and are used in the treatment of pulmonary hypertension.