Distribution and neurochemical characterisation of neurons containing neuregulin 1 in the enteric nervous system within the porcine small intestine.

Introduction: The enteric nervous system (ENS) in the wall of the gastrointestinal tract is complex and comprises many neurons, which are differentiated in terms of structure, function and neurochemistry. Neuregulin 1 (NRG 1) is one of the neuronal factors synthesised in the ENS about the distribution and functions of which relatively little is known. The present study is the first description of the distribution of NRG 1 in the ENS in various segments of the porcine small intestine.

Material and methods: Fragments were excised from the duodenum, jejunum and ileum of five euthanised Piétrain × Duroc sows, 18-20 kg in weight and eight weeks of age. Paraformaldehyde-fixed and dehydrated tissue was sectioned and double-labelling immunofluorescence was performed using Alexa Fluor-conjugated secondary antibodies to visualise neuregulin 1 and its colocalisation with vasoactive intestinal polypeptide (VIP), galanin (GAL), and the neuronal isoform of nitric oxide synthase (nNOS) in the myenteric and inner and outer submucosal plexuses, with PGP 9.5 serving as a pan-neuronal marker.

Results: Neuregulin 1 was observed in all enteric plexuses in each segment of the small intestine. The percentage of NRG 1-positive neurons ranged from 8.38 ± 0.55% of all neurons in the jejunal inner submucous plexus to 21.52 ± 0.98% in the duodenal myenteric plexus. Cells which were NRG 1-positive also contained VIP, GAL and nNOS in all segments of the small intestine to a degree which varied by small intestine segment and enteric plexus type.

Conclusion: The results indicate that NRG 1-positive neurons are present in the ENS of the porcine small intestine and differ significantly neurochemically, which may suggest a multifaceted role for NRG-1 in the controlling of the small intestine activity.