A. Schematic diagram of a sagittal section through a rat head at embryonic day (E) 14.
Sagittal tissue sections hybridized with cRNA for brain-derived neurotrophic factor (BDNF;
B, C), and neurotrophin-3 (NT3; D-F). BDNF mRNA is low in olfactory epithelium (OE)
from E14 (B) to E20 (C). High levels of NT3 mRNA are seen at E14 (D) and E16 (E),
but decrease by E20 (F). Moderate levels occur in cortex (CX), and high levels are seen in
olfactory bulb (OB) by E16. LV, lateral ventricle; BTel, basal telencephalon; Tg,
tegmentum; CB, cerebellum; on, olfactory nerve; CCx, cingulate cortex.