The Study of the Physiology and Pharmacology of the Human Cutaneous Microcirculation By Capillary Microscopy and Television Cinematography

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Abstract
Visual observation, capillary microscopy, and the newly adapted method of television cinephotomicrography have been applied to the study of some aspects of the physiology and pharmacology of the human cutaneous microcirculation. Certain vascular phenomena have been observed and the following conclusions can be drawn. Vasomotion, resulting from precapillary constriction and dilatation with secondary changes in capillary blood flow, occurs in some human cutaneous capillaries. There is no evidence for intrinsic contractility of the cutaneous capillaries, and all changes in caliber and blood flow are secondary to changes in pre- and postcapillary muscular vessels. Epinephrine and norepinephrine act locally as venoconstrictors as well as arterial constrictors in human skin, with epinephrine apparently having the more potent effect. Angiotensin II, known to be a potent precapillary constrictor, has little or no effect on cutaneous veins, and causes a less profound blanch than do the catecholamines. Mecholyl and related cholinergic agents are potent vasodilators, increasing flow rates in cutaneous capillaries and abolishing vasomotion. Serotonin, a known venoconstrictor, causes an unusual cyanotic response in human skin. This apparently results from constriction of larger cutaneous veins with resulting stasis in the subpapillary plexus. The cyanosis is enhanced by admixture with epinephrine or norepinephrine as a result of the synergistic and potentiating effects of these agents.