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 transfo rming growth-factor-(TGF-) beta-family, is an essential factor for the deve lopment of the enteric nervous system (ENS) during embryogenesis. In the pr esent study, the effects of GDNF on postnatal ENS development were investig ated using cultures of myenteric plexus from the small intestine of newborn albino rats of different developmental phases (P1, P7, P14). Myenteric ple xus 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 s erum-free medium containing various doses (1, 10, 100 ng/ml) of GDNF. The e ffect of the neurotrophic factor was evaluated using parameters such as cel l size, neuronal survival, or neurite elongation. While neither glial-cell nor neuronal size was influenced by GDNF, there was an observable effect up on 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. Alread y 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 observa tions suggest that GDNF plays an important role not only in pre-, but also in postnatal development of the enteric nervous system.