Fig. 4. Distribution of perivascular sympathetic nerve fibers in the ileal wall. Hematoxylin-eosin staining (A ) shows the different layers:1 = longitudinal muscularis propria, 2 = circular muscularis propria, 3 = submucosa, 4 = mucosa. Tyrosine hydroxylase-positive immunofluorescence shows sympathetic nerve fibers (arrowheads ) in the muscularis (B  and C ) and submucosa (D ). No sympathetic nerve fibers were identified in the mucosa of the ileum (D ). Scale bars = 20 μm.