Neurovascular Interface in Porcine Small Intestine: Specific for Nitrergic rather than Nonnitrergic Neurons

Abstract

In the 1970s, by using classic histological methods, close topographical relationships between special areas of enteric ganglia and capillaries were shown in the pig. In this study, by application of double and triple immunohistochemistry, we confirmed this neurovascular interface and demonstrated that these zones are mainly confined to nitrergic neurons in the myenteric and the external submucosal plexus. In the upper small intestine of the pig, the respective neurons display type III morphology, i.e. they have long, slender and branched dendrites and a single axon. In another set of experiments, we prepared specimens for electron-microscopical analysis of these zones. Both ganglia and capillaries display continuous basement membranes, the smallest distances between them being 1,000 nm at the myenteric and 300 nm at the external submucosal level. The capillary endothelium was mostly continuous but, at the external submucosal level, scattered fenestrations were observed. This particular neurovascular relationship suggests that nitrergic neurons may require a greater amount of oxygen and/or nutrients. In guinea pig and mouse, previous ischemia/reperfusion experiments showed that nitrergic neurons are selectively damaged. Thus, a preferential blood supply of enteric nitrergic neurons may indicate that these neurons are more vulnerable in ischemia.

Unique Neural Circuit Connectivity of Mouse Proximal, Middle, and Distal Colon Defines Regional Colonic Motor Patterns

“…There is a capillary network that sends blind-end vessels near to the plexi, but that occasionally do go around and/or through a ganglion ( Figure 13 D2–D4 ). Similar to what has been reported for nitrergic neurons, 46 we did identify vascular nets or baskets around some calretinin expressing myenteric neurons ( Figure 13 E1 , arrowheads) as well as unidentified neurons ( Figure 13 E1 , arrows).

Figure 13 The colonic vasculature parallels the overall colonic tissue architecture.

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“…We visualized the colonic neurovascular complex using CD31 to label endothelial cells or DyLight 488-tomato Lectin to paint the vessels. 45 , 46 The colonic vascular network derives from the superior and inferior mesenteric artery and vein ( Figure 13 A ), with branches that do not appear to be region-specific ( Figure 13 B and C ). The colonic vasculature parallels the overall tissue architecture, with the primary branches running circumferentially, and arterioles, venules, and capillaries running longitudinally and circumferentially ( Figure 13 D1 , D2 , F1 , and F2 ).…”