Effect of r-HuD antisense treatment on neurite outgrowth in PC12 cells. A, Control PC12 cells treated with NGF for 4 d. B, PC12 cells treated with NGF and r-HuD antisense oligonucleotides for 4 d. C, PC12 cells treated with NGF and unrelated AC6 antisense oligonucleotides. D, PC12 cells treated with NGF and sense r-HuD oligonucleotides for 4 d. Scale bar, 20 μm.