Excitatory and inhibitory enteric innervation of horse lower esophageal sphincter

Abstract

The lower esophageal sphincter (LES) is a specialized, thickened muscle region with a high resting tone mediated by myogenic and neurogenic mechanisms. During swallowing or belching, the LES undergoes strong inhibitory innervation. In the horse, the LES seems to be organized as a "one-way" structure, enabling only the oral-anal progression of food. We characterized the esophageal and gastric pericardial inhibitory and excitatory intramural neurons immunoreactive (IR) for the enzymes neuronal nitric oxide synthase (nNOS) and choline acetyltransferase. Large percentages of myenteric plexus (MP) and submucosal (SMP) plexus nNOS-IR neurons were observed in the esophagus (72 ± 9 and 69 ± 8 %, respectively) and stomach (57 ± 17 and 45 ± 3 %, respectively). In the esophagus, cholinergic MP and SMP neurons were 29 ± 14 and 65 ± 24 vs. 36 ± 8 and 38 ± 20 % in the stomach, respectively. The high percentage of nitrergic inhibitory motor neurons observed in the caudal esophagus reinforces the role of the enteric nervous system in the horse LES relaxation. These findings might allow an evaluation of whether selective groups of enteric neurons are involved in horse neurological disorders such as megaesophagus, equine dysautonomia, and white lethal foal syndrome.

Ex vivoultrasonographic and histological morphometry of small intestinal wall layers in horses

“…Worth 10 already described this line by ex vivo US in the wall of the ileum, while more recently it was found also in the other small and large intestinal tracts, albeit not consistently, by means of a high‐frequency transducer 8 . Histologically, such additional ultrasonographic line was consistent with connective and nerve tissues of the myenteric plexus and intrinsic and extrinsic nerve fibers, interposed between the LML and CML of the tunica muscularis 16–18 . Overall, on histological assessment, our findings (i.e., muscularis mucosae , Peyer's patches, and myenteric plexus) agreed with morphological data of the equine small intestinal wall reported in the literature 19–21 .…”

Cannabinoid and Cannabinoid-Related Receptors in the Myenteric Plexus of the Porcine Ileum

“…The ileum was harvested within 30 min from the animals' deaths and was longitudinally opened along the mesenteric border. The tissues were then washed in phosphatebuffered saline (PBS), fixed, and processed to obtain longitudinal (2.0 cm × 0.5 cm) and tangential cryosections (2.0 cm × 1.0 cm), which were later processed for immunohistochemistry, as previously described [30].…”

Zinc Transporter 3 (Znt3) as an Active Substance in the Enteric Nervous System of the Porcine Esophagus

“…Its organization depends on animal species and the part of the GI tract (Timmermans et al 1997; Brown and Timmermans 2004). In esophagus and stomach, the ENS consists of the following two kinds of intramural ganglia: myenteric ganglia (MG), which are connected to each other by density network of nerves and create myenteric plexus located between the longitudinal and circular muscle layers, as well as submucous ganglia (SG), which not form a plexus and situated near the lamina propria of the mucosal layer (Teixeira et al 2001; Zacharko-Siembida and Arciszewski 2014; Chiocchetti et al 2015; Rekawek et al 2015). The same types of enteric ganglia are present in small and large intestine of rodents, but contrary to esophagus and stomach, also submucous ganglia form plexus (Paulino et al 2011).…”