Fig. 1.

GR inhibits Bdnf expression in 9-day PCN. a, Bright field microscopy showed that PCN developed a morphology with multiple cellular processes on Day 3 in vitro (D3 IV, upper panel), while a denser neuronal network was visible on Day 9 (D9 IV); magnification x10. b, Total BDNF mRNA expression was significantly repressed by DEX. Relative expression of total BDNF mRNA assessed by qPCR on exon IX under vehicle, (Veh, ethanol) dexamethasone (DEX; 10^-7 M) or DEX and GR antagonist RU486 (RU; 10^-6 M) treatments (1 h). Results are expressed as attomol of BDNF mRNA/attomol of 36B4 mRNA (n = 6, Mean ± SEM); * Veh vs DEX, P < 0.05; $ DEX vs DEX + RU, P < 0.05, Mann Whitney U-tests. c, Schematic representation of mouse Bdnf gene according to Aid et al [18]. Eight untranslated exons (I to VIII) splice onto one common coding exon IX, with two regulatory regions that drive the expression of mainly 2 clusters of untranslated exons (I, II, III and IV, V, VI, respectively). d, Relative expression of Bdnf untranslated exons in 9-day PCN (n = 6, Mean ± SEM) as measured by RT-qPCR. Exons IV and VI containing transcripts are the most expressed isoforms, followed by that of exon I containing mRNA. ND: non determined. e, f, g, h, i, Expression of exon I, IV, and VI containing transcripts was downregulated by DEX while expression of exon VII and VIII containing transcripts was not modified by DEX treatment. qPCR analyses of exon I, IV VI, VII and VIII mRNA levels in the same samples than in (a), Mean ± SEM; * (P < 0.05) vs Veh; $P < 0.05; $$ P < 0.01 vs DEX; Mann Whitney U-tests