Effects of enriched environment (EE) on expression of brain-derived neurotrophic factor (BDNF) transcripts and protein levels in the hippocampus. (a) Quantitative reverse transcriptase (qRT)-PCR results showing total BDNF mRNA levels (protein-coding exon IX, n=4 per group). (b) qRT-PCR results showing mRNA levels of BDNF exons I, IIa, IIb, IIc, III, IV, VI, VIII and IXa in the hippocampus (HIP). Results are expressed as % wild-type-standard condition (WT-SC) for WT-EE and % knock-in IV (KIV)-SC for KIV-EE. Note that EE significantly increased levels of total BDNF mRNA levels in both genotypes through multiple promoters. (n=4 per group). (c) Enzyme-linked immunosorbent assay (ELISA) quantification of BDNF protein levels in the HIP. Note that the BDNF protein levels were reduced in BDNF-KIV mice in SC compared with WT mice in SC. BDNF protein levels were increased in BDNF-KIV mice in EE compared with those in SC (n=12 per group). *P<0.05; **P<0.01.