Neurochemical differentiation of rat enteric neurons during pre- and postnatal life

Abstract

The presence of nitric oxide synthase (the enzyme which synthesizes nitric oxide), vasoactive intestinal peptide (VIP) and pituitary adenylyl-cyclase-activating peptide (PACAP) in the rat enteric nervous system between term (E18) and 90 days postpartum (P90) was investigated by immunohistochemistry. Neuronal maturity was ascertained by emanining for the presence of two novel neuron intermediate filament proteins: alpha-internexin, which is transiently expressed in developing neurons, and peripherin, which is expressed in differentiating as well as in mature neurons. The alimentary canal of the foetus at E18, unfed newborn, suckling, weaning and adult rats was studied. Throughout the rat gut the myenteric neurons were recognized by the time the foetal stage was reached and the submucous neurons by the suckling period. alpha-Internexin was present at E18; its levels increased during ageing and were markedly reduced at P30. Peripherin was first detected at birth; its levels increased with ageing and practically almost all of the neurons and nerve fibres were labelled from P30. Nitric oxide synthase was present at E18 and the number of labelled neurons gradually increased with ageing, while both VIP and PACAP could be detected by the end of the suckling period in an equal number of neurons to that in adulthood. These data indicate that in the rat gut the onset of the mature neuronal phenotype is not yet achieved at birth and that the neurochemical differentiation is accomplished during the first month of postnatal life.

Postnatal development of myenteric neurochemical phenotype and impact on neuromuscular transmission in the rat colon

“…This development of the ENS is also associated with a time-dependent differentiation of specific neurochemically identified neuronal populations that has been described mainly in the prenatal period of mice (28). In rats, 5-HT expression appears early during the embryonic life whereas other mediators appear later such as nitric oxide (NO) by E18, VIP during the suckling period, and PACAP-27 during the weaning period (13). A recent study has also shown an increase in the vesicular acetylcholine transporter (VAChT) immunoreactivity in the mouse pup, which was correlated with the development of colonic migrating motor complexes (CMMCs) (19).…”

Morphological Features of the Esophageal Enteric Nervous System and Its Stereological Changes during Aging

“…Our results are even more striking but still in line with these fi ndings, indicating that about three fourths (64-82%) of the myenteric neurons in the esophagus of adult rats were NADPH-d positive [9] . This proportion is much higher than those found in the other parts of the rat GI tract, where myenteric nitrergic neurons were found at lower proportions: 29-38% in the stomach [22] , 28% in the duodenum, 15-27% in the ileum [23,24] and 12-57% in the colon [25] . High proportions of esophageal myenteric nitrergic neurons have also been demonstrated in other species, such as cats (48-60%), opossums (35-51%) [7,26] , pigs (63%) [2,11] , monkeys (45%) [18] and even humans (55%) [27] .…”

Temporal and regional morphological differences as a consequence of FGF-2 deficiency are mirrored in the myenteric proteome

“…Several clinical and experimental observations suggest that homeostatic control of gut function in a changing environment might be achieved through adaptive changes occurring in the enteric ganglia [34]. Recent studies in infants and children [35] indicate that the density of ganglion cells in the myenteric plexus decreases significantly with age during the first 3-4 years of life and that the neurochemical differentiation in rat is accomplished during the first month of postnatal live [17]. In rat also the total number of enteric neurons decreases significantly after birth [29].…”