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FIG. 2. Expression of BDNF mRNA in the developing diencephalon and optic tectum, and its relation with projecting and arborizing
optic nerve fibers. Transverse cryostat sections of stage 45 tadpoles hybridized in situ with an antisense BDNF probe (A, C, E) are compared
with equivalent sections of sibling embryos in which optic nerve fibers were anterogradely labeled from the retina with the lipophylic
dye, DiI (B, D, F). (A) A transverse� oblique section at the level of the optic tract (B; arrowhead) shows digoxygenin-positive cell bodies
over dorsomedial, dorsolateral, as well as ventromedial cellular diencephalic regions. (C�F) Hybridization of transverse cryostat sections
at the level of the developing optic tectum shows individual digoxygenin-positive cell bodies that lay dorsolaterally (C, E), in close
proximity to the tectal neuropil (np). Note that cell bodies are all restricted to the central gray matter region, while DiI fiber labeling is
restricted to the neuropil formed of arborizing optic nerve fibers (D, F; diffuse DiI label) and mesencephalic neuritic processes (G; retrogradely
labeled with biotin�dextran). High BDNF-expressing cell bodies also localize to the ventral mesencephalic nuclei (C), just dorsal
to the infundibulum (if). (E�G) High-magnification photomicrographs at the level of the optic tectum show some intensely stained
digoxygenin-positive cell bodies (E; black arrow) that lay in close proximity to branching retinal arbors (F; white arrow). As seen by the
retrograde label with biotin�dextran, this population of tectal cells project their dendrites (G; arrowhead) to the tectal neuropil, where
RGC axons arborize. Dorsal is up, ventral is down. Scale bar, 50 mm. |
