VIP and pulmonary arterial hypertension: Vasoactive intestinal peptide (VIP) has been shown to reduce the pulmonary arterial pressure in rabbit with monocrotaline-induced pulmonary arterial hypertension[29] and also in healthy human subjects.[30] Decreased levels of VIP in serum and lung have been noted in patients with PAH and treatment with inhaled VIP has also been shown to improve the hemodynamics and clinical course in these patients.[31]