The GDNF-induced neurite outgrowth and neuronal survival in dissociated myenteric plexus cultures of the rat small intestine decreases postnatally.

Glial cell-line-derived neurotrophic factor (GDNF), a member of the transforming growth-factor-(TGF-) beta-family, is an essential factor for the development of the enteric nervous system (ENS) during embryogenesis. In the present study, the effects of GDNF on postnatal ENS development were investigated using cultures of myenteric plexus from the small intestine of newborn albino rats of different developmental phases (P1, P7, P14). Myenteric plexus was dissociated and cultivated as mixed cultures of enteric neurons and glial cells. After seeding, the cultures were kept for 24 h or 7 days in serum-free medium containing various doses (1, 10, 100 ng/ml) of GDNF. The effect of the neurotrophic factor was evaluated using parameters such as cell size, neuronal survival, or neurite elongation. While neither glial-cell nor neuronal size was influenced by GDNF, there was an observable effect upon neuronal survival and neurite elongation. The cultures treated with GDNF displayed increased neurite outgrowth. The promoting effect was dose- and age-dependent, decreasing clearly during the early postnatal period. Already after 24 h, neuronal survival was increased in P1 and P7, but not in P14 cultures. In long-term cultures, a marked tendency to form cell aggregates and dense fiber networks was observed when treated with GDNF. These observations suggest that GDNF plays an important role not only in pre-, but also in postnatal development of the enteric nervous system.