Mechanisms in the Return of Vascular Tone Following Sympathectomy in Man

The response of the hand blood vessels has been determined to the intra-arterial administration of ephedrine and reserpine and to the intravenous administration of norepinephrine before and at intervals after sympatheetomy. The constrictor response to ephedrine slowly disappeared over a period of six weeks, during which time the vessels became increasingly sensitive to norepinephrine. The dilator effect of reserpine was abolished early after sympatheetomy but became slowly re-established over the subsequent three months. The findings suggest that residual vasoconstrictor fibers cannot account for the return of tone following sympatheetomy but that changes in the catecholamine content of the tissue and increasing sensitivity to both these and circulating amines may be closely related to this phenomenon.