Double labeling of vagal preganglionic and sympathetic postganglionic fibers in celiac ganglion, superior mesenteric arteries and myenteric plexus.

Sympathetic efferents regulate the “fight-or-flight” response and sympathetic and vagal fibers have been suggested to retrogradely and centrally spread pathogens associated with Parkinson’s disease. To examine the arrangement of the vagal and sympathetic motor fibers in the celiac ganglion (CG), gastrointestinal tract, and along the superior mesenteric artery and its sub-branches, we double-labeled the vagal efferents by injecting Dextran-Texas Red into the dorsal motor nucleus of the vagus and the sympathetic postganglionics with tyrosine hydroxylase immunohistochemistry in male Sprague-Dawley rats (n = 18). The laser scanning confocal microscope was used for image analysis. Vagal nerve endings were densely distributed around the CG neurons, and the right CG received more. Vagal and sympathetic efferent endings formed various ring or string shapes that tangled closely in the myenteric plexus of the forestomach, duodenum, jejunum and ileum. Vagal and sympathetic efferents coursed within the same nerve bundles before reaching the myenteric plexus, had in-apposition varicosities, and ran parallel with the superior mesenteric artery and its sub-branches. Although a complete sympathetic tracing and an incomplete tracing and/or damage to the vagal preganglionic neurons may lead to a sampling bias, the sympathetic innervations in the blood vessels and myenteric plexus are stronger than in the vagus. The in-apposition innervation varicosities of the vagal and sympathetic efferents within the same nerve bundles and in the myenteric plexus of the gut with complex innervation patterns may offer a network to automatically control gastrointestinal functions and an infection route of the Parkinson’s disease between the autonomic efferent endings.