Fig. 5. Explants on coronal forebrain sections.A, A fluorescence-labeled explant is shown attached to the amygdala (amg) with its neurite halo sharply inhibited at the border (black arrows) with the optic tract (ot). A single neuron is shown (black arrowhead) with the neurite extending on, and in parallel with, the optic tract. B, Fluorescence-labeled explants are shown attached directly to the optic tract with extensive outgrowth on, and in parallel with, the tract (black arrows). Outgrowth from explants on the optic tract is comparable in length with that of explants on neocortex (ctx; black arrowhead). Neurite outgrowth on portions of the optic tract sectioned transversely is more mixed in orientation (white arrow). The outgrowth halo of a detached explant (white arrowhead) is shown having grown on the amygdala but inhibited by the adjacent optic tract. C, A fluorescence-labeled explant is shown attached to the corpus callosum (cc) with extensive outgrowth extending on, and in parallel with, the tract. As neurites approach the cingulum (cg), they become increasingly mixed in orientation. D, The same field shown in C is shown with phase-contrast optics.cp, Caudate-putamen. Scale bars: A, 100 μm; B, 250 μm; C, D, 100 μm.