ABSTRACT
Adolescence is a critical period of development. It is very likely that there is significant maturation of the enteric nervous system (ENS) of the gut during this stage of life, especially since there are substantial changes in factors known to influence the ENS including diet and microbiota during this time, but this remains unknown. To examine maturation of the ENS during adolescence, we performed immunohistochemistry using advanced microscopy and analytical methods to compare enteric neurons and glia of the duodenum and colon of mice taken prior to weaning with those of young adult mice. We found significant changes in the architecture of both myenteric and submucosal plexuses and surprisingly found subsets of enteric cells that co-expressed the pan-neuronal marker, Hu, and either glial markers Sox10 or S100ß, not both. About 70% and 35% of all Hu â+ âneurons in the submucous plexus of the young adult duodenum and colon respectively also expressed S100ß. The proportion of Hu+/Sox10 â+ âcells in the duodenal myenteric plexus decreased, while the proportion of Hu+/S100ß+ cells in the colonic submucosal plexus increased during adolescence. In the submucous plexus, there were significant increases in the proportions of vasoactive intestinal peptide+ and choline acetyltransferase â+ âsecretomotor neurons, of neurofilament M (NFM)+ neurons in the colon and of calretinin â+ âneurons in the duodenum during adolescence. There were no age-dependent changes in the neurochemistry of various myenteric neuronal subtypes, including those immunoreactive for neuronal nitric oxide synthase (nNOS), Calbindin, Calretinin or NFM. There were significant increases in the somata sizes of Calretinin â+ âsubmucosal and myenteric neurons, and nNOS â+ âmyenteric neurons, and these enteric neurons received significantly more synaptophysin â+ âcontacts onto their cell bodies during adolescence. This is the first study showing that enteric neurons and glia in the gut undergo significant changes in their anatomy and chemistry during adolescence. Notably changes in synaptic contacts within the enteric circuitry strongly suggest maturation in gastrointestinal function occurs during this time.
