Brief Review Nonadrenergic Neural Vasodilator Mechanisms

Vasomotor influences mediated through periph-eral nerves were first demonstrated byClaude Bernarde. After many decades of ex-perimentation, few doubt that the sympathetic outflow mediated through norepinephrine and epinephrine is the major physiological vasomotor mechanism. How-ever, nonadrenergic nerves supply most regional vas-cular beds, and their possible influence must be taken seriously. In this review, we survey the evidence for functional nonadrenergic dilator innervation of regional vascular beds in common laboratory animals and man with par-ticular emphasis on the neurotransmitters involved. The available evidence is classified here with respect to the long acknowledged criteria for the establishment of a neuroeffector transmitter. Simply stated, these criteria require that a putative transmitter substance 1