The distribution of serotonin-immunoreactive (5HT-IR) nerve cells and fibers was thoroughly investigated immunohistochemically in the rat stomach, duodenum, jejunum, ileum, and colon. The immunoreactivity of the 5HT neurons was compared between non-treated controls and animals treated with colchicine, colchicine plus 5-hydroxytryptophan (5HTP), colchicine plus pargyline, and reserpine. The intensity of immunoreactivity in nerve fibers as well as nerve cell bodies was enhanced mostly in colchicine plus pargyline treated animals, therefore these animals were used for an observation of precise localization of 5HT in the rat gastrointestinal (GI) tract. Immunoreactivity in the nerve cell bodies and fibers was completely abolished in the GI tract of reserpine treated animals. The pattern of localization and projection of 5HT-IR neurons was similar in all segments of the rat GI tract: 5HT-IR nerve cell bodies were located in the myenteric plexus and showed the distinctive features of Dogiel type I neurons. Prominent bundles of varicose fibers traversed the myenteric ganglia and some of them surrounded the cell bodies of immunopositive and immunonegative neurons. 5HT-IR nerve fibers were located in the submucous plexus, densely entwined about the submucosal blood vessels. Most characteristically, 5HT-IR nerve fibers invaded the lamina propria of mucosa where they underlay the crypt epithelium. In conclusion, the present study showed that 5HT-IR neurons located in the myenteric plexus projected fibers widely in the rat GI tract. The localization of fibers in the lamina propria of mucosa implies that this neuron may exert an important role in the epithelial function of the GI tract.

Flow-mediated dilation (FMD) of brachial artery provides a noninvasive assessment of coronary endothelial dysfunction. Acetylcholine (ACh) has been used as an agent for estimating coronary endothelial function. In contrast to ACh, there is no evidence for a relationship between FMD and coronary vasodilation to bradykinin (BK). The aim of this study was to compare the flow-mediated vasodilation of brachial artery with coronary vasomotor responses to intracoronary ACh or BK in patients with an angiographically normal left anterior descending coronary artery. Ninety-one patients underwent the cardiac catheterization examination with coronary endothelial function testing and the brachial ultrasound study. BK (0.2, 0.6, 2.0 microg/min) and ACh (3, 10, 30 microg/min) were administered into the left coronary artery in a stepwise manner. Coronary blood flow was evaluated by the Doppler flow velocity measurement. Coronary diameters were measured by the quantitative coronary angiography. The assessment of endothelial function in the brachial artery was made in response to reactive hyperemia with high-resolution ultrasound. Bradykinin induced dose-dependent increases in epicardial coronary diameter and blood flow. There was a significant positive correlation between FMD- and BK-induced vasodilations of epicardial coronary arteries (0.2 microg/min: r = 0.30; 0.6 microg/min: r = 0.42; 2.0 microg/min: r = 0.44, P < 0.01, respectively) and resistance coronary arteries (0.2 microg/min: r = 0.40; 0.6 microg/min: r = 0.56; 2.0 microg/min: r = 0.59, P < 0.0001, respectively). FMD correlated with ACh-induced vasomotions of resistance but not epicardial coronary arteries. No correlation was seen between nitroglycerin-induced brachial artery vasodilation and BK-induced coronary vasodilation. The endothelial dysfunction of peripheral arteries correlated well with that of the coronary arteries especially vasomotor responses to BK.

The plasma level of oxLDL is an appropriate surrogate for assessing coronary endothelial-dependent vasomotor function as estimated by responses to BK compared with conventional risk factors for atherosclerosis.

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