Expression pattern of BDNF and TrkB in dorsal pons. A–C, Representative examples of emulsion-dipped coronal sections of adult wild-type mice hybridized with TrkB cRNA (A) and BDNF cRNA (B, C). Notice very strong TrkB mRNA expression over the locus ceruleus (A, arrows) and BDNF mRNA-expressing cells in ventrolateral position to IVth ventricle (B, C, arrows). D–F show coronal sections of mice carrying a lacZ reporter knock-in into the endogenous BDNF locus (Farinas et al., 2001). Sections were double stained with Texas Red-labeled lacZ and FITC-labeled TH immunoreactivity.D, Dorsal pons in area of the LC; E, higher magnification of D;arrow inD and E points to the same neuron.F, Dorsal medulla in the area of A2.Arrow in F points to double-labeled neuron (TH+, lacZ+). Notice lack of double-labeled neurons in the LC (D, E).CBL, Cerebellum; asterisk, IVth ventricle. Images taken at 2 × 10 magnification inA; 4 × 10 magnification in B, C; 10 × 10 magnification in D; 100 × 10 magnification in E, F.