JNK phosphorylation was assayed by measuring phosphoJNK immunofluorescence (IF) in growth cones (A) or somata (B,C), at 30 min (A,B) or 6 h (C) after shift from 25K to one of the following experimental conditions: 25K control; 5K DMEM lacking neurotrophic factors; 5K with 100 ng/ml NT-3; 5K with 20 μM SP600125 (SP). The data were normalized to phosphoJNK IF in the 5K condition in each experiment. JNK phosphorylation is significantly elevated in growth cones within 30 min of trophic factor deprivation by shift to 5K but the increase is prevented by NT-3 or by SP600125. In contrast, JNK phosphorylation is not elevated in somata 30 min after shift to 5K but is elevated 6 h after shift. Statistical significance of differences relative to 5K was determined by ANOVA with Tukey-Kramer correction (*p<0.05, **p<0.01, ***p<0.001).