Relationship between noradrenaline-induced depolarization and contraction in vascular smooth muscle

In strips of rabbit main pulmonary artery, full dose-response curves of noradrenaline for the mechanical and electrical responses of the vascular smooth muscle cells were obtained under normal conditions and after increasing and decreasing the membrane potential with strychnine and tetraethylammonium, respectively. The results suggest that the magnitude of the noradrenaline-induced contraction is related to the height of the membrane potential and not to the degree of depolarization produced by the adrenergic transmitter.