Northern blot analysis of oligonucleotide probes designed for the present study. The probes for BDNF and trkA were hybridized onto the total RNA obtained from naive L4 DRG, and the probe for βNGF was hybridized onto the total RNA obtained from the sciatic nerve 14 d after L5 SPNL. Each probe was hybridized at the position or positions expected from the previous studies (see Materials and Methods). The top and bottom arrows indicate the positions of 28S and 18S rRNAs, respectively.