Sympathetic vasodilatation in human limbs.

This review focuses on recent developments in our understanding of active vasodilatation in human skin and skeletal muscle. We have attempted to place recent advances in their historical context and review the evolution of thinking on active vasodilatation in these two vascular beds. In human skin, active vasodilatation is well established, but the neurotransmitter responsible for the dilatation is unknown. In human skeletal muscle, older studies provided circumstantial evidence consistent with sympathetically mediated vasodilatation, but the evidence was never unambiguous. By contrast, recent studies on active vasodilatation in human skeletal muscle in conjunction with a reinterpretation of data from previous studies casts doubt on the existence of sympathetic vasodilator fibres in human skeletal muscle.