Pulmonary hypertension, a common complication of several wide-spread diseases, like COPD, collagen disorders, viral infections or congenital heart defects, is still a challenge for clinical treatment strategies. A variety of ion channels and intracellular messengers are known to be involved in the development of increased pulmonary blood pressure but the nature of the differences between the pulmonary and the systemic circuit remains elusive to date.

Therefore, aim of our work is to determine differences in vascular tone regulation of isolated pulmonary arteries and the aorta of mouse using isometric force measurements. The pulmonary arteries proved more sensitive to the canonical vasoconstrictors like norepinephrine, phenylephrine and serotonin. Interestingly, high physiological concentrations of norepinephrine caused a strong vasorelaxation of pulmonary arteries precontracted with phenylephrine. Thus, in the pulmonary artery norepinephrine influences vascular tone independently from a1-receptors.