Effect of Pinacidil on Norepinephrine- and Potassium-Induced Contractions and Membrane Potential in Rat and Human Resistance Vessels and in Rat Aorta: PDF OnlyVidebaek Lars M.; Aalkjaer, Christian; Mulvany, Michael J.Journal of Cardiovascular Pharmacology: 1988 - p S23-S29 Free Abstract Summary: The effect of pinacidil on contractile responses to norepinephrine, potassium, and membrane potential was examined in rat and human resistance vessels. In some experiments rat aorta was also used. Pinacidil (0.1-30 μM) caused a concentration-dependent relaxation of norepinephrine-induced contractions in all vessels studied. In the same concentration range, pinacidil had only little effect on potassium (125 mM) activated rat mesenteric and femoral resistance vessels. In denervated rat mesenteric resistance vessels, a depolarization with potassium (125 mM) before superimposing a norepinephrine tone markedly diminished the effect of pinacidil. In resting rat mesenteric resistance vessels, pinacidil (1-10 μM) caused a hyperpolarization of 10-15 mV. In rat aorta, pinacidil (10 μM) caused a significant (p < 0.001) increase in 86Rb+ efflux rate constant whereas 1 μM had no effect. The results of these experiments indicate that the vasodilating effect may be caused by a hyperpolarization of the vascular smooth muscle cell membrane. Address correspondence and reprint requests to L. M. Videbaek at Biophysics Institute, Aarhus University, 8000 Aarhus C, Denmark. © Lippincott-Raven Publishers.