Fig. 2.

Time course of the survival of P-neurons in cultures supplemented with NGF or bFGF from animals of different ages. A, Average percentage (±SEM) of surviving P-neurons as a function of DIV, relative to their number at 1 DIV (taken as 100%), in cultures established from rats of ages E18, P2, and P5. The cultures were maintained in defined media alone (squares) or defined media supplemented with 50 ng/ml NGF (white circles) or 10 ng/ml bFGF (black circles). Each plot contains data from three experiments. NGF but not bFGF promoted the survival of E18 neurons (left panel). The reversed result was obtained with P5 neurons (right panel). At P2 (middle panel), the factors had similar effects. Analysis of the data at 2–5 DIV (ANOVA, and Tukey post hoc test;p = 0.05) indicated highly significant statistical differences (asterisks) between the NGF treatment and bFGF treatment or control (E18), between NGF or bFGF treatment and control (P2), and between bFGF treatment and NGF or control (P5). B, Dose–response curve of the average survival (±SD) of P-neurons from P5 animals (estimated at 3 DIV) as a function of bFGF concentration (n = 2). C, The survival-promoting effect of NGF (50 ng/ml) on E20 P-neurons was completely blocked byTrk-A kinase activity inhibitor K252a (50 nm) (n = 2). The barsindicate the percentage of survival (±SD) after 4 DIV in defined media alone (C) or supplemented with NGF (N), K252a (K), or both (N + K) at the concentrations specified above. K252a prevents the effect of NGF in a statistically significant way (see asterisk).