Ca²⁺-dependent dendritic transport of ID4 mRNA. (A and B) ID4-chimeric α-tubulin mRNA was delivered to dendrites of sympathetic neurons after β-adrenergic activation with isoproterenol. (C and D) In contrast, little dendritic transport was observed when the β-adrenergic agonist isoproterenol was applied after preincubation with the intracellular Ca²⁺ chelator BAPTA-AM. Number of cells analyzed: (A and B) 16 cells, 67 dendrites; (C and D) 15 cells, 60 dendrites. Bar, 50 µm. (E) Quantitative analysis. One-way ANOVA, Dunnett’s post hoc analysis (comparison of RNA levels in the basal state [Fig. 2] with RNA levels after β-adrenergic activation and with levels after β-adrenergic activation in the presence of BAPTA-AM): comparison with isoproterenol (A and B), P < 0.001 for all interval points; comparison with isoproterenol/BAPTA-AM (C and D), P > 0.8 for interval points 50 µm. Error bars indicate SEM.