Cocaine-mediated induction of PDGF-BB in vivo. (A) Cocaine administration resulted in increased expression of PDGF-BB (red, bottom) in isolated microvesssels (Caveolin [Cav-1] positive, green) compared with saline-injected animals (top). PDGF-BB: red; Cav-1: green; nuclei: blue; n = 4 per group; Scale bar: 20 μm. (B) Western blot analysis of lysates from isolated microvessels from cocaine-administered mice demonstrated increased expression of PDGF-BB compared with saline-injected animals. (C) Egr-1^−/− mice treated with cocaine failed to up-regulate PDGF-BB in the isolated microvessels. (D) Pretreatment of mice with PDGF-BB neutralizing antibody ameliorated cocaine-mediated increase in BBB permeability. Mannitol-treated group was used as a positive control. (E) Cocaine administration resulted in increased BBB permeability in WT but not in the Egr-1^−/− mice. All the data are presented as mean ± SD, n = 6 per group. *P < .05 vs saline group; #P < .05 vs cocaine group. (F) Schematic of the signaling pathways involved in cocaine-mediated induction of PDGF-BB in HBMECs. Exposure of cocaine leads to σ receptor-mediated activation of ERK1/2, JNK, p38 MAPKs and PI3K/Akt signaling pathways. However, ERK1/2 and JNK MAPKs but not p38 MAPK or PI3K/Akt signaling result in the subsequent activation of the downstream transcription factor, Egr-1. Activation of Egr-1, in turn, leads to enhanced PDGF-BB expression.