Microscopic observations on the action of histamine on small blood vessels.

Abstract

Studies have been made by microscopic observation of blood vessels in skin, skeletal muscle, mesentery and intestinal wall. In cats anesthetized with pentobarbital sodium, the effects of histamine upon the diameters of small blood vessels have been observed and it has been found that, in general, larger microscopic vessels respond to topically and intravenously applied histamine by constriction, whereas smaller venules and arterioles, in general, respond by dilation. After blood vessels have been constricted by continuous infusions of epinephrine or sympathetic stimulation, the administration of histamine induces a dilation. Mesenteric and intestinal small veins are more sensitive to histamine than are small arterioles in the same structures.