Spatiotemporal expression of BDNF in the hippocampus induced by the continuous intracerebroventricular infusion of β-amyloid in rats

Abstract

The β-amyloid protein (Aβ) is the major component of senile plaques found in the brain in Alzheimer’s disease (AD). Its neurotoxic properties in vivo, however, are not well defined. Since the expression of neurotrophin genes is considered an important component of the intrinsic neuroprotective response to insults, we analyzed the gene expression of neurotrophins in the brains of rats which received a continuous infusion of Aβ-(1–42) into the cerebroventricle. Northern blot analysis revealed a significant increase in brain-derived neurotrophic factor (BDNF) expression in the hippocampus but no change in the cerebral cortices. The alteration peaked on days 3–7 and returned to the basal level on day 14 after the start of Aβ-(1–42) infusion. No significant changes in nerve growth factor or neurotrophin-3 mRNA expression were observed. The infusion of Aβ-(1–40) and (25–35) also triggered the expression of BDNF mRNA, whereas neither Aβ-(40–1) nor (1–16) had any effect. In situ hybridization histochemistry revealed that the expression mainly occurred in the hilus and granular layer of the dentate gyrus and to a lesser extent in the pyramidal neurons of the CA1 region. These results demonstrate that the continuous intracerebroventricular infusion of Aβ induces selective and spatiotemporal expression of BDNF mRNA in the hippocampus.