Morphometric characteristics of intramural autonomic nerve ganglia of the myenteric and submucosal plexuses of the small and large intestines in rats during postnatal ontogenesis

BACKGROUND: The morphology of intramural autonomic nerve ganglia of the myenteric (MP) and submucosal (SP) plexuses of the intestine in adult animals has been studied in sufficient detail, whereas data on age-related features of these structures remain limited. AIM: This study aimed to investigate the morphometric characteristics of intramural autonomic nerve ganglia of the myenteric and submucosal plexuses of the small and large intestines in rats during postnatal ontogenesis. METHODS: The study used male Wistar rats of different age groups: newborns; 10, 20, 30, and 60 days after birth; and 12 and 24 months of age. Immunohistochemical analysis was performed using fluorescently labeled antibodies to protein gene product 9.5 (PGP9.5). RESULTS: During postnatal ontogenesis, the number of ganglia per 1 mm2 decreases, whereas the ganglion area increases in both the small and large intestines. The mean area of nerve ganglia in the MP of the small and large intestines increases from birth up to day 60, whereas in the SP, this increase occurs during the first 30 days of life. The mean density of ganglia per 1 mm2 in the MP decreases during the first 60 days in the small intestine and during 12 months in the large intestine. In the SP, this parameter decreased in both the small and large intestines during the first 60 days of life. The mean number of PGP9.5-immunoreactive neurons per ganglion in the MP remains unchanged during postnatal ontogenesis, whereas in the SP, it increases during the first 10 days after birth. CONCLUSION: In postnatal ontogenesis, during the first 30 days of life, the size of ganglia in the MP and SP increases, whereas their density per unit surface of the small and large intestines decreases. The shape of ganglia and the number of neurons in the MP ganglia do not change during postnatal ontogenesis. In contrast to the MP of the small and large intestines in rats, the SP ganglia remain immature at birth, with the formation of the SP ganglion network during the first 10 days after birth.