Fig. 2. Growth of different axon populations in response to the notochord in collagen gel co-cultures. (A-E) Dark-field photomicrographs of representative co-cultures. (A,B) Stage 36 (St36) DRG explants (n=90 and 36, respectively); (C,D) Stage 26-27 (St26) DRG explants (n=55 and 34, respectively); (E) Stage 36 SCG explants (n=28). Explants were cultured with NGF (A,C,E) or with NT3 (B,D). (F) Histogram showing the mean repulsion score±s.e.m. for neural explants co-cultured with stage 17-21 notochord. Asterisk indicates no significant repulsion. Scale bar: 100 µm.