Localization of specialized noradrenaline receptors at neuromuscular junctions on arterioles of the guinea-pig.

1. Noradrenaline was applied by ionophoresis to various positions on the surface of an arteriole, and any changes in membrane potential of the arteriolar smooth muscle were recorded. 2. At a proportion of positions noradrenaline produced membrane depolarization. 3. The positions where noradrenaline produced these membrane potential changes were restricted to regions close to the sympathetic nerves which innervated the arterioles.