Embryonic chick DRGn were cultured on fresh-frozen sections of normal adult rat sciatic nerve pretreated with buffer only (Control), MMP-2, or chondroitinase ABC (Ch’ase), as described in Materials and Methods. DRGn were grown on nerve sections in DMEM/N2^+NGFmedium for 48 hr, and the assay was terminated by aldehyde fixation. The chick DRGn were immunolabeled with an anti-chick N-CAM monoclonal antibody, and the length of the single longest neurite per neuron was measured. In random fields, >50 neurons were scored on multiple sections in three experiments. Data represent the means ± SD. Statistical significance was determined by Student’s ttest. *p < 0.0001.