Intrinsic innervation of the ileocaecal junction in the horse: preliminary study.
BACKGROUND
In horses, morpho-functional studies related to the enteric nervous system (ENS) controlling the sphincters are lacking.


OBJECTIVE
To investigate immunohistochemically the morphology, distribution, density, phenotypes and projections of neurons controlling the ileocaecal junction (ICJ).


METHODS
Two young horses were anaesthetised and underwent midline laparotomy. The neuronal retrograde fluorescent tracer Fast Blue (FB) was injected into the wall of the ICJ. A post surgical survival time of 30 days was used. Following euthanasia, the ileum and a small portion of caecum were removed. Cryosections were used to investigate the immunoreactivity (IR) of the neurons innervating the ICJ for choline acetyltransferase (ChAT), neuronal nitric oxide synthase (nNOS), substance P (SP), calcitonin gene-related peptide (CGRP) and neurofilament NF200kDa (NF).


RESULTS
Ileal FB-labelled neurons innervating the ICJ were located in the myenteric plexus (MP) and submucosal plexus (SMP) up to 48 cm and 28 cm, respectively, from the point of the FB injections. Descending MP and SMP neurons were nitrergic (54 +/- 11% and 68 +/- 4%, respectively), cholinergic (60 +/- 19% and 82 +/- 11%, respectively), NF-IR (54 +/- 9% and 78 +/- 21%, respectively), and SP-IR (about 20% in both the plexuses). CGRP-IR was expressed only by SMP descending neurons (45 +/- 21%). In both the plexuses descending neurons coexpressing nNOS- and ChAT-IR were also observed (25 +/- 11% and 61 +/- 27%, respectively).


CONCLUSIONS
The presence of ileal long projecting neurons innervating the ICJ suggests that they are critical for its modulation. Consequently, in bowel diseases in which the resection of the terminal jejunum and proximal ileum are required, it is preferable, whenever possible, to conserve the major portion of the ileum.


CONCLUSIONS
The knowledge of the phenotype of ENS neurons of the ileum might be helpful for developing pharmaceutical treatment of the ICJ motility disorders.
Chiocchetti
R
R
Department of Veterinary Morphophysiology and Animal Productions, University of Bologna, 40064 Ozzano Emilia, Bologna, Italy.
Bombardi
C
C
Mongardi Fantaguzzi
C
C
Russo
D
D
Venturelli
E
E
Montoneri
C
C
Spadari
A
A
Romagnoli
N
N
Grandis
A
A
D000578:Amidines; D000818:Animals; D002432:Cecum / Q000294:innervation*; D006736:Horses / Q000033:anatomy & histology* / Q000502:physiology; D007082:Ileum / Q000294:innervation*; D007150:Immunohistochemistry / Q000662:veterinary; D009474:Neurons / Q000166:cytology / Q000502:physiology; D013194:Staining and Labeling
D000578:Amidines; C031455:diamidino compound 253-50