Ephedrine in the cat lung vasculature

Background: Ephedrine is one of the most commonly used non-catecholamine sympathomimetic agents. It is used in operating rooms and critical care settings worldwide. While it has many side effects, its ability to rapidly raise blood pressure makes it an ideal agent to maintain homeostasis as well as in emergency situations. While its effects are known to be mediated by an alpha-mediated mechanism, the exact alpha subtype is unknown. In addition, no studies using ephedrine have been performed in the pulmonary vascular bed of the cat. Methods: The effects of phentolamine, a non-selective alpha-receptor blocker, and prazosin, an alpha(1) -selective antagonist, were investigated on pulmonary arterial responses to ephedrine, phenylepherine, norepinephrine, and U-46619. Lobar arterial perfusion pressure was continuously monitored, electronically averaged, and recorded with constant flow in the isolated left lower lobe vascular bed of the cat. Results: Phentolamine and prazosin significantly reduced vasoconstrictor pulmonary perfusion pressure increases induced by ephedrine. Conclusion: Ephedrine has significant vasopressor activity in the pulmonary vascular bed of the cat meditated predominantly by alpha1 adrenergic receptor activation.