Vagal nerve stimulation causes noncholinergic dilatation of gastric arterioles

Vagal nerve stimulation causes prompt dilatation of gastric submucosal arterioles (the vessels that control gastric mucosal blood flow) in rats. In vivo microscopy was used to determine whether this direct vasodilator effect of vagal nerve stimulation on rat gastric submucosal arterioles is mediated by cholinergic fibers. Acetylcholine and atropine were topically applied to the submucosa. The distal end of the severed vagus nerve was electrically stimulated (8 V, 2 ms, 6 Hz, 20 s) subdiaphragmatically. Diameter changes of the submucosal arterioles were videotaped and measured with an image-splitting technique on playback of the videotapes. Acetylcholine, 10(-7) to 10(-5) M, dilated the arterioles dose dependently. Atropine prevented the acetylcholine-induced dilatation, 10(-5) M, nearly completely inhibiting the dilatation. Vagal nerve stimulation dilated the arterioles promptly, and this dilatation was not blocked by 10(-5) M atropine, a dose that blocked the acetylcholine-induced dilatation. These results indicate that vagal nerve stimulation causes atropine-resistant, noncholinergic dilatation of gastric submucosal arterioles in rats.