Correlated morphological and chemical phenotyping in myenteric type V neurons of porcine ileum.
The study was aimed at the immunohistochemical characterization of myenteric Stach type V neurons of the pig ileum that were not included in the widely used Dogiel classification. So far, this conspicuous population has been defined morphologically on the basis of silver-impregnated specimens only. By using neurofilament immunohistochemistry, type V neurons that occur singly or in aggregates could be identified unequivocally and could be distinguished from other smoothly contoured myenteric neurons, i.e., type II and type IV. Double-labeling immunohistochemistry revealed a number of potentially neuroactive substances or their synthesizing enzymes to be present in type V neurons. Choline acetyltransferase immunoreactivity (-ir) was found in all type V neurons, whereas neuronal nitric oxide synthase was detected in none. Leu-enkephalin-ir was found within 92.3%, somatostatin (SOM)-ir within 91.1%, calcitonin gene-related peptide (CGRP)-ir within 80.6% and met-enkephalin-ir within 74.7% of type V neurons. Triple-labeling immunohistochemistry was applied to address the question of a specific chemical coding for myenteric type V neurons. In contrast to other combinations of neuroactive substances/enzymes that were found in both type V and other, nontype V neurons, SOM/CGRP-ir was the only combination observed exclusively within type V neurons. Both substances were colocalized in 79.3% of type V neurons. This colocalization discriminates four-fifths of the type V neurons chemically from both type II neurons (CGRP positive, SOM negative) and type IV neurons (CGRP negative, SOM positive), which both share, at first glance, a similar morphology with type V neurons. These results further support the concept of a close correlation between morphologically defined neuronal type and chemical coding and, it is likely, also function in the enteric nervous system of larger mammals.
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D004743:Enkephalin, Leucine / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000378:metabolism; D005260:Female; D007082:Ileum / Q000166:cytology / Q000294:innervation* / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D009197:Myenteric Plexus / Q000166:cytology* / Q000502:physiology; D016900:Neurofilament Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology* / Q000502:physiology*; D009479:Neuropeptides / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D013004:Somatostatin / Q000378:metabolism; D013552:Swine / Q000033:anatomy & histology* / Q000502:physiology
D016900:Neurofilament Proteins; D009479:Neuropeptides; D013004:Somatostatin; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D002795:Choline O-Acetyltransferase; D015740:Calcitonin Gene-Related Peptide