Figure 2.

Projection patterns of cholinergic neurons in selected target tissues. ChAT-expressing neurons were labeled in their entirety, thus allowing us to visualize their projections patterns in the periphery. A: For instance, fluorescence was seen in preganglionic parasympathetic fibers in the airways (20× 5 optical plans, 1.2-μm step). Of note, intrinsic cholinergic neurons and scattered epithelial cells were also found in the airways (arrowheads). B: Abundant innervation of postganglionic origin was also seen in the pancreas (20×, 6 optical plans, 1.3-μm step). C: Preganglionic sympathetic neurons innervated sympathetic ganglia such as the mesenteric ganglion (20×, 5 optical sections, 0.92-μm step). Asterisks are positioned over the cell profiles of putative postganglionic target neurons. As previously noted in the superior cervical ganglion, a few postganglionic sympathetic neurons appear to be cholinergic (arrowhead). D: The adrenals contained a large fiber supply (20×, 5 optical plans, 0.92-μm step). As a note, the fluorescence apparent in chromaffin cells corresponded to non-specific autofluorescence (seen in every filter and in wild-type animals). E: Although many large blood vessels throughout the body contained innervation, that of the abdominal aorta was particularly rich. F: The projections of cholinergic somatomotor neurons was visible as reflected by the labeling of neuromuscular junctions in the forepaw. Arrows indicate fluorescently labeled neuronal fibers, and arrowheads point to representative cell bodies. Abbreviations: crc, chromaffin cells; m, medulla; NMJ, neuromuscular junction. Scale bar = 50 μm in A; 20 μm in B (applies to B–D); 50 μm in E; 100 μm in F.