mRNA levels of BDNF transcripts in hippocampus of rats treated with antidepressants. Rats given i.p. injections of an antidepressant for 21 days. Animals were sacrificed 2 h after the last antidepressant injection. Values are the mean ± S.D. from 6 rats. Antidepressant-treated group was compared with sham group. Overall group differences were: exon I, df = 3,20, F = 25.1, P <0.001; exon II, df = 3,20, F = 15.4, P <0.001; exon III, df = 3,20, F = 53.7, P <0.001; exon IV, df = 3,20, F = 68.4, P <0.004. * P <0.001.