The causal involvement of the BDNF-TrkB pathway in dentate gyrus in early-life stress-induced cognitive deficits

Abstract

Cognitive dysfunction is a significant, untreated clinical need in patients with psychiatric disorders, for which preclinical studies are needed to understand the underlying mechanisms and to identify potential therapeutic targets. Early-life stress (ELS) leads to long-lasting deficits of hippocampus-dependent learning and memory in adult mice, which may be associated with the hypofunction of the brain-derived neurotrophic factor (BDNF) and its high-affinity receptor, tropomyosin receptor kinase B (TrkB). In this study, we carried out eight experiments to examine the causal involvement of the BDNF-TrkB pathway in dentate gyrus (DG) and the therapeutic effects of the TrkB agonist (7,8-DHF) in ELS-induced cognitive deficits. Adopting the limited nesting and beding material paradigm, we first demonstrated that ELS impaired spatial memory, suppressed BDNF expression and neurogenesis in DG in adult mice. Down-regulating BDNF expression (conditional BDNF knockdown) or inhibition of the TrkB receptor (using its anatognist ANA-12) in the DG mimicked the cognitive deficits of ELS. Acute up-regulation of BDNF (exogenous human recombinant BDNF microinjection) levels or activation of TrkB receptor (using its agonist, 7,8-DHF) in the DG restored ELS-induced spatial memory loss. Finally, acute and subchronic systemic administration of 7,8-DHF successfully restored spatial memory loss in stressed mice. Subchronic 7,8-DHF treatment also reversed ELS-induced neurogenesis reduction. Our findings highlight BDNF-TrkB system as the molecular target of ELS-induced spatial memory deficits and provide translational evidence for the intervention at this system in the treatment of cognitive deficits in stress-related psychiatric disorders, such as major depressive disorder.