PROTEIN EXTRACTS FROM THE GUT WALL INFLUENCE THE POSTNATAL-DEVELOPMENT OF RAT MYENTERIC NEURONS IN-VITRO

Neurons migrating from the neural crest into the presumptive gut wall need an appropriate microenvironment to survive and differentiate duri ng ontogenesis. The rate enteric nervous system (ENS) keeps developing beyond birth. The aim of this study was to investigate the neurotroph ic effects of the postnatal microenvironment. Myenteric plexus was iso lated from the smooth muscle layer of newborn rats at different ages ( postnatal day (p)1, p7, p14) and grown as dissociated cell cultures. T he culture medium (hormone-supplemented, serum-free) was supplemented either with glial-cell-line-derived-neurotrophic factor (GDNF) or with protein extracts from homogenized smooth muscles layer of p7 rats. Cu ltures kept in defined medium alone were used as controls. After 18 h in vitro both GDNF and protein extract had a neuritogenic effect upon p1 and p7 neurons, while p14 neurons were only stimulated by the prote in extracts. The GDNF effect upon these neurons did not differ signifi cantly from the effects in defined medium alone. The average neurite o utgrowth in extract-supplemented cultures was always longer than that seen in those treated with GDNF. Although GDNF influences the postnata l development of myentric neurons in vitro it could not be detected im munohistochemically either in Western blots of the protein extracts or in cryostat sections of the gut. (C) 1998 Elsevier Science Ireland Lt d.