Figure 1.

Schematic overview of the existing theories on the (cholinergic) anti-inflammatory pathway. The theory of the cholinergic anti-inflammatory pathway calls for the efferent fibers to suppress inflammation via the splenic nerve bundles. The nerve bundles that innervate the spleen are sympathetic in nature, although cholinergic innervation of the superior pole of the murine spleen was also described (via an apical nerve [20]). Figure 2 displays how the splenic nerve can influence immune cells. It is hypothesized that vagal fibers and the splenic nerve synapse in the celiac ganglion (CG), however, thus far, anatomical studies have not established this. An alternative theory assumes that the greater splanchnic nerves comprise the anti-inflammatory pathway [21]. Both sympathetic and cholinergic nerves innervate the large intestine (Figure 3), although the distal part only receives innervation from the sympathetic nerves that originate from the sacrum. SMG—superior mesenteric ganglion; SMN—superior mesenteric nerves.