Autonomic Nerves in the Precapillary Vessel Wall

A wide variety of substances are utilized as neurotransmitters in perivascular autonomic nerves, including noradrenaline, acetylcholine, ATP, 5-hydroxy-tryptamine, and a number of peptides. A general model for the autonomic innervation of the vessel wall is outlined, and variations in the innervation patterns in different precapillary vessels are described. Evidence that noradrenaline and ATP are cotransmitters in some precapillary vessels is presented. In the rat tail artery, ATP appears to be responsible for the fast depolarizations that are recorded in response to perivascular nerve stimulation, whereas noradrenaline is responsible for the slow, maintained depolarization.