Vascular Reactions in the Small Intestine during Vasodilatation

The reactions within the consecutive vascular sections of the small intestine of the cat were studied during vasodilatations induced by secretin and cholccystokinin, infused i.a. or released “endogenously”, or by transmural electrical field and mucosal mechanical stimulations. All these potentially “physiological” stimuli evoked a response pattern similar to that of i.a. infused 5‐hydroxytryptamine and characterized by a relaxation of the resistance vessels as well as of the precapillary “sphincters”, as reflected in an increased capillary filtration coefficient. A small increase of regional blood volume was also observed during most vasodilatations. On the basis of these experiments it is impossible to exclude any of the abovementioned mechanisms in the discussion of the cause of the functional hyperemia of the gut. It is proposed that this vasodilatation depends partly upon a release of intestinal hormones, partly upon local mechanisms evoked by mechanical and possible also by chemical stimulation of the intestinal mucosa.