Fig. 1. Tissue distribution and clearance of infused BDNF. BDNF (2 μg/2 μl, 25 min) was infused into stratum lacunosum-moleculare CA1, immediately above the hippocampal fissure, ∼300 μm above the medial perforant path→granule cell synapses. Cytochrome c (Cyt C) was infused as a protein control. Brains were obtained at 15 min or 1, 3, 6, or 24 hr after infusion, and coronal sections were immunostained for BDNF.A, Schematic depiction of cannula–electrode assembly in the hippocampus. B, C, BDNF immunostaining obtained at 15 min and 1 hr after BDNF infusion, respectively. BDNF was rapidly delivered and cleared from the dentate gyrus. D, Cyt C 15 min control. B–D were taken through the area of the cannula tract. The BDNF antibody titer for the BDNF-infused brains was 1:20,000 (minimizing endogenous staining and facilitating detection of exogenous protein). The antibody titer for Cyt C-infused brains was 1:10,000 (therefore darkerstaining of mossy fibers). Scale bar, 1 mm.