Quantitative changes of nitrergic neurons during postnatal development of chicken myenteric plexus

Information regarding the development of the enteric nervous system (ENS) is important for understanding the functional abnormalities of the gut. Because fertilized chicken eggs provide easy access to embryos, chicken models have been widely used to study embryonic development of myenteric plexus; however, no study has been focused on the postnatal period. The aim of this study was to perform a qualitative and quantitative analysis of the nitrergic neurons in the myenteric plexus of developing chickens in the postnatal period.

Whole-mount preparations of the myenteric plexus were made in 7-d, 15-d, and 40-d old (adult) chickens of either sex (n=15). The myenteric plexus was studied after nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry using light microscopy, digital photography, and Image-Pro Plus 6.0 software. The numbers of positively stained neurons and ganglia were counted in the duodenum, jejunum, ileum, caecum, and colon in the different age groups. Data were expressed as mean±standard deviation (SD), and statistical analysis was performed using a one-way analysis of variance (ANOVA) test.

The positively stained neurons showed various morphologies and staining intensities, and formed bead-shaped and U-shaped arrangements in the myenteric plexus. The densities of neurons and ganglia increased with age. However, the number of positive neurons per ganglion increased. The number of NADPH-d-positive neurons was highest in the colon, followed by the ileum, the jejunum, the duodenum, and the caeca in all age groups.

Developmental changes in the myenteric plexus of chickens continue in the postnatal period, indicating that the maturation process of the gastrointestinal function is gradual. In addition, no significant difference is happening among different intestinal segments during postnatal development, suggesting that the function of different intestinal segments had been determined after birth.