Fig. 2.

Effects of RA on the induction of responsiveness to GDNF and neurturin (NTN). SCG neurons were cultured in the presence of the indicated concentrations of GDNF or neurturin without or with 10⁻⁷m RA for 4 d before neuronal survival was examined. The number of viable neurons was counted and expressed as in Figure1B. Each value represents the mean and SD (n = 3). *p < 0.05, **p < 0.01 compared between RA-treated and untreated neurons (Student's t test).