An Investigation into the Postnatal Development of the Enteric Nervous System.

Jones, Sarahlouise (1999). An Investigation into the Postnatal Development of the Enteric Nervous System. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000ff5b

Abstract

The postnatal development of the myenteric plexus from the rat ileum was studied using a variety of techniques. Immunohistochemistry of wholemount preparations for the neural marker PGP 9.5, revealed changes in the density of myenteric neurons during postnatal development. A significant increase in neuronal numbers was observed between 7 and 14 days. NADPH diaphorase positive neurons were among those that increased in number during this time. Total neuronal numbers decreased significantly between 14 and 21 days, possibly indicating a period of naturally occurring cell death. There was no change in the number of NADPH diaphorase positive neurons during this time. A second significant increase in neuronal numbers was observed between 21 and 28 days. Total neuronal numbers appeared to stabilise at 35 days. Ultrastructural analysis revealed early postnatal (7 day) neuron and glial profiles to be relatively mature and exhibit a similar variety of shapes as seen in the adult rat and guinea pig. The basal lamina that surrounds most adult myenteric ganglia, was found to be developmentally acquired. The number of smooth muscle cells increased between 7 and 21 days, then numbers stabilised and the thickness of the smooth muscle increased. Possible stimuli for the observed changes in the myenteric plexus include GDNF, a neurotrophic factor that is expressed in postnatal intestinal muscle. GDNF was found to stimulate an increase in the number of myenteric neurons and neurite outgrowth in culture. GDNF did not however, influence other aspects of myenteric neuronal growth such as somal size, suggesting that other molecules may also be involved in the postnatal development of myenteric neurons. In summary, the work presented in this thesis has highlighted the plasticity of the postnatal enteric nervous system and the importance of the postnatal period in establishing the adult pattern of innervation and diversity of phenotypes.