Regulation of amygdala-dependent learning by brain-derived neurotrophic factor is mediated by extracellular signal-regulated kinase and phosphatidylinositol-3-kinase

Neuropsychopharmacology. 2006 Feb;31(2):287-96. doi: 10.1038/sj.npp.1300830.


This study is designed to characterize the signal cascades by which brain-derived neurotrophic factor (BDNF) modulates long-term memory of fear conditioning. Enzyme-linked immunosorbent assay (ELISA) and Western blot analysis of tissue homogenates taken from fear-conditioned rats showed an increase in the amygdala of BDNF protein levels and its receptor TrkB phosphorylation. Bilateral administration of a TrkB ligand scavenger TrkB IgG and a Trk-specific tyrosine kinase inhibitor K252a to the amygdala impaired fear memory, as measured with fear-potentiated startle. Fear conditioning resulted in the association of Shc and TrkB, Shc and Ras, the increase in active Ras and phosphorylation of mitogen-activated protein kinase (MAPK). Treatment of amygdala slices with BDNF for 15 min increased the levels of active Ras, and MAPK and Akt phosphorylation. BDNF-induced MAPK phosphorylation was completely abolished by MEK inhibitors, and was partially inhibited by farnesyltransferase or phosphatidylinositol-3 kinase (PI-3 kinase) inhibitors. On the other hand, BDNF-induced Akt phosphorylation was unaffected by farnesyltransferase or MEK inhibitors, but could be blocked by PI-3 kinase inhibitors. Together, these data suggest a requirement of BDNF for fear learning. The memory-enhancing effect of BDNF involves the activation of MAPK and PI-3 kinase. BDNF-induced MAPK phosphorylation in the amygdala is mediated via TrkB and the Shc-binding site. Shc binding to TrkB leads to activation of Ras, Raf, and MEK. In addition, BDNF could induce phosphorylation of MAPK via activation of PI-3 kinase.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amygdala / drug effects
  • Amygdala / physiology*
  • Animals
  • Antibodies / pharmacology
  • Behavior, Animal
  • Blotting, Western / methods
  • Brain-Derived Neurotrophic Factor / metabolism*
  • Brain-Derived Neurotrophic Factor / pharmacology
  • Conditioning, Psychological / drug effects
  • Conditioning, Psychological / physiology*
  • Electroshock / methods
  • Enzyme Inhibitors / pharmacology
  • Extracellular Signal-Regulated MAP Kinases / immunology
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • Fear
  • Gene Expression / drug effects
  • Immunoprecipitation / methods
  • In Vitro Techniques
  • Male
  • Monomeric GTP-Binding Proteins / pharmacology
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphorylation / drug effects
  • Rats
  • Rats, Sprague-Dawley
  • Reflex, Startle / drug effects
  • Reflex, Startle / physiology
  • Time Factors


  • Antibodies
  • Brain-Derived Neurotrophic Factor
  • Enzyme Inhibitors
  • Extracellular Signal-Regulated MAP Kinases
  • Monomeric GTP-Binding Proteins