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Morphology and Neurochemistry of Descending and Ascending Myenteric Plexus Neurons of Sheep Ileum
Author(s) -
Mazzuoli Gemma,
Mazzoni Maurizio,
Albanese Valeria,
Clavenzani Paolo,
LalattaCosterbosa Giovanna,
Lucchi Maria L.,
Furness John B.,
Chiocchetti Roberto
Publication year - 2007
Publication title -
the anatomical record: advances in integrative anatomy and evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.678
H-Index - 62
eISSN - 1932-8494
pISSN - 1932-8486
DOI - 10.1002/ar.20615
Subject(s) - myenteric plexus , descending colon , enteric nervous system , choline acetyltransferase , ascending colon , biology , ileum , anatomy , cecum , chemistry , central nervous system , medicine , endocrinology , immunohistochemistry , immunology , rectum , ecology
The specific patterns of gastrointestinal motility in large herbivores may relate to differences in the organization of enteric nerve circuits, compared with other mammals. To investigate this possibility, we characterized the morphologies, chemical phenotypes, and projections of myenteric plexus (MP) neurons of the sheep ileum. Morphologies and projections were investigated after application of the carbocyanine dye (1,1′, di‐octadecyl‐3,3,3′,3′,‐tetramethylindo‐carbocyanine perchlorate, DiI) to fixed tissues. To study chemical phenotypes, the fluorescent tracer Fast Blue (FB) was injected into the wall of the ileum, in vivo, 12–14 cm oral to the ileo‐caecal junction. Over 80% of the descending and ascending DiI‐labeled neurons had typical Dogiel type I morphology, whereas only a few Dogiel type II neurons were observed. Nevertheless, there were long projections (up to 10 cm) of Dogiel type II neurons in both directions. Both type II and type I neurons were neurofilament immunoreactive (IR). We observed long projections of descending (up to 18 cm) and ascending (up to 12–14 cm) FB‐labeled MP neurons. Nitric oxide synthase (NOS)‐IR, peripheral choline acetyltransferase (pChAT)‐IR, and substance P (SP)‐IR occurred in both descending and ascending myenteric neurons. NOS‐IR was in approximately 60% of FB‐labeled descending and ascending neurons, whereas those expressing pChAT‐IR were 67 ± 15% and 60 ± 14%, respectively. Descending neurons expressing SP‐IR were 48 ± 15% and ascending were 56 ± 12%. NOS‐IR and pChAT‐IR, and SP‐IR and pChAT‐IR were commonly colocalized in both ascending and descending pathways. In descending pathways, almost all SP‐IR neurons were also pChAT‐IR (98 ± 3%) and NOS‐IR (99 ± 2 NOS + /SP + /pChAT − ). Many FB‐labeled descending neurons showed both NOS‐ and pChAT‐IR. Descending neurons may represent inhibitory motor neurons (NOS + /SP + /pChAT − ) and two classes of interneurons (pChAT + /NOS − , and pChAT + /NOS + /SP + ). In ascending pathways, most neurons are pChAT + /NOS + /SP + . Thus, in sheep, ascending interneurons and ascending excitatory motor neurons both have the same phenotype, and other markers are needed to distinguish them. Anat Rec, 2007. © 2007 Wiley‐Liss, Inc.