Measurements of the membrane potential of arterial smooth muscle in anesthetized animals and its relationship to changes in artery diameter.

Intracellular recordings of membrane potential were made from the smooth muscle of small (90-200 micron i.d.) arteries in the ears of anaesthetized guinea pigs and rabbits. Perivascular nerve stimulation evoked excitatory junction potentials and action potentials in the smooth muscle. No spontaneous muscle action potentials were recorded. Local block of perivascular nerve activity with tetrodotoxin caused a vasodilatation and a small hyperpolarization of the smooth muscle. Prazosin caused a smaller vasodilatation and no hyperpolarization. It was concluded that some of the nerve-mediated arterial tone may be caused by noradrenaline acting alpha 1-receptors, and some by some other mechanism.