Adrenergic sensitivity of different-size gastric submucosal arterioles

A gradation in the vasoconstriction response to norepinephrine has been reported in the rat mesentery, smaller arterioles being more sensitive than larger ones. The purpose of this investigation was to determine if this is also true of the rat gastric submucosal arterioles, the vessels which control gastric mucosal blood flow. The response of different-diameter gastric submucosal arterioles to the topical application of norepinephrine was studied. Arteriolar diameter changes were studied using in vivo microscopy with an image-splitting technique. Responses were expressed as percentage change from basal diameter. In response to topical norepinephrine all arterioles studied demonstrated constriction, escape, and poststimulation dilatation. The constriction responses of the precapillary arterioles (less than 10 mu in diameter) and the larger arterioles (up to 79 micrometers) were of similar magnitude. The precapillary arterioles, however, dilated significantly more than larger ones in the poststimulation period. These studies show that, unlike the rat mesentery, there is no gradation in sensitivity to norepinephrine constriction in the rat gastric submucosal arterioles.