Neurotrophin-3 increases neurite outgrowth and apoptosis in explants of the chicken neural plate.

This study examined the effect of neurotrophin-3 (NT-3) on neurite outgrowth and apoptosis of chicken neural plate explants prior to neural tube formation. In situ hybridization revealed that mRNA for the full-length (catalytic) NT-3 receptor, TrkC, was present in, and limited to, the neural plate (including the neural folds) coincident with its formation. Neural plate explants were maintained in vitro on a collagen gel under serum-free conditions in the presence or absence of exogenous NT-3 and/or an antibody to NT-3. In the absence of exogenous NT-3, explants exhibited neurite outgrowth after several days in vitro; apoptotic cells were also seen after 2 days in vitro. This does not appear to be due to endogenous NT-3, since the total number of neurites or apoptotic cells was unchanged if explants were exposed to an NT-3 antibody for the entire culture period. In the presence of exogenous NT-3, neural plate explants exhibited a dose-dependent statistically significant increase in the total number of neurites as compared to explants maintained under control conditions, as well as a statistically significant increase in apoptosis. These NT-3 effects were blocked by an NT-3 antibody. In contrast, NT-3 had no effect on the length of neurites. These findings suggest that NT-3 may play a role during early neural development in vivo.