Calcitonin gene-related peptide in morphologically well-defined type II neurons of the enteric nervous system in the porcine small intestine.

The morphological classification of the different neuronal cell types is generally accepted and expanded by us; nevertheless, immunohistochemically and electrophysiologically the existence of clear-cut categories of enteric neurons is frequently questioned. The immunohistochemical results demonstrated in this study, however, provide the first direct link between a morphological type of enteric neuron and an immunohistochemical staining for a distinct peptide. Evidence demonstrates that calcitonin gene-related peptide occurs in only one morphologically defined type of neuron, viz., in type II neurons, and can therefore be regarded as a 'marker peptide' for type II neurons. Hence, the present immunohistochemical findings illustrate the validity of the morphological classification of the enteric neurons.