Quantification of nitrergic neurons in the myenteric plexus of gastric antrum and ileum of healthy and diabetic dogs

- The density of myenteric neurons was not significantly reduced in diabetic (DM) dogs.
- HuC/HuD immunolabeling showed nuclear dislocation in DM dogs.
- nNOS-IR myenteric neurons were significantly reduced in the ileum of DM dogs.
- nNOS-IR nervous fibers were significantly reduced in the muscular layers of DM dogs.
- Some ileal ganglia of DM dogs showed thickening of the periganglionic connective tissue.

Diabetes mellitus (DM) determines a wide array of severe clinical complications including gastrointestinal motility disorders. The present study investigates the effects of spontaneous DM on the intramural innervation and in particular on nitrergic neurons of the myenteric plexus (MP) of the canine gastric antrum and ileum. Specimens of antrum and ileum from eight control-dogs and five insulin-dependent DM-dogs were collected. MP neurons were immunohistochemically identified with the anti-HuC/HuD antibody, while nitrergic neurons were identified with the antibody anti-neuronal nitric oxide synthase (nNOS). The density of HuC/HuD-immunoreactive (IR) neurons was determined and the nitrergic neurons were quantified as a relative percentage, in consideration of the total number of HuC/HuD-IR neurons. Furthermore, the density of nitrergic fibers in the muscular layers was calculated. Data were expressed as mean ± standard deviation. Compared to control-dogs, no significant differences resulted in the density of HuC/HuD-IR neurons in the antrum and ileum of DM-dogs; however, HuC/HuD-immunolabeling showed nuclear localization and fragmentation in DM-dogs. In the stomachs of control- and DM-dogs, the percentages of nitrergic neurons were 30 ± 6% and 25 ± 2%, respectively (P = 0.112). In the ileum of the control-dogs, the percentage of nitrergic neurons was 29 ± 5%, while in the DM-dogs, it was significantly reduced 19 ± 5% (P = 0.006). The density of nNOS-IR nervous fibers was meaningful reduced in either the tracts considered. Notably, the ganglia of DM-dogs showed also a thickening of the periganglionic connective tissue. These findings indicate that DM in dogs induce modification of the myenteric neurons and, in particular, of the nitrergic neuronal subpopulation.

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