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Keywords:

  • hippocampus;
  • mice;
  • neurotrophins;
  • Reelin;
  • Schizophrenia;
  • sex hormones

Abstract

Neurodevelopmental psychiatric disorders such as schizophrenia may be caused by a combination of gene × environment, gene × gene, and/or gene × sex interactions. Reduced expression of both Reelin and Brain-Derived Neurotrophic factor (BDNF) has been associated with schizophrenia in human post-mortem studies. However, it remains unclear how Reelin and BDNF interact (gene × gene) and whether this is sex-specific (gene × sex). This study investigated BDNF-TrkB signaling in the hippocampus of male and female Reelin heterozygous (Rln+/−) mice. We found significantly increased levels of BDNF in the ventral hippocampus (VHP) of female, but not male Rln+/− compared to wild-type (WT) controls. While levels of TrkB were not significantly altered, phosphorylated TrkB (pTrkB) levels were significantly lower, again only in female Rln+/− compared to WT. This translated to downstream effects with a significant decrease in phosphorylated ERK1 (pERK1). No changes in BDNF, TrkB, pTrkB or pERK1/2 were observed in the dorsal hippocampus of Rln+/− mice. Ovariectomy (OVX) had no effect in WT controls, but caused a significant decrease in BDNF expression in the VHP of Rln+/− mice to the levels of intact WT controls. The high expression of BDNF was restored in OVX Rln+/− mice by 17β-estradiol treatment, suggesting that Rln+/− mice respond differently to an altered estradiol state than WT controls. In addition, while OVX had no significant effect on TrkB or ERK expression/phosphorylation, OVX + estradiol treatment markedly increased TrkB and ERK1 phosphorylation in Rln+/− and, to a lesser extent in WT controls, compared to intact genotype-matched controls. These data may provide a better understanding of the interaction of Reelin and BDNF in the hippocampus, which may be involved in schizophrenia.