Vasoactive intestinal peptide as a possible transmitter of nonadrenergic, noncholinergic relaxation of pulmonary...

Electrical field stimulation of isolated guinea pig pulmonary artery induced a brief initial contraction followed by a more prolonged relaxation. alpha-Adrenergic blockade prevented the contraction and enhanced the relaxation. beta-Adrenergic and cholinergic muscarinic blockade partially reduced the relaxation, but 44.4% of the relaxation persisted after adrenergic and cholinergic blockade. The PA relaxation was associated with the release of immunoreactive VIP, both before and after this blockade. Tetrodotoxin abolished the nonadrenergic, noncholinergic relaxation and markedly reduced the release of VIP. This relaxation was similarly attenuated by a monoclonal antibody against VIP.