Brain-Derived Neurotrophic Factor-Dependent Unmasking of "Silent" Synapses in the Developing Mouse Barrel Cortex

• Published in: Proceedings of the National Academy of Sciences - PNAS 2003-10, Vol.100 (22), p.13069-13074
• Main Authors: Itami, Chiaki, Kimura, Fumitaka, Kohno, Tomoko, Matsuoka, Masato, Ichikawa, Masumi, Tsumoto, Tadaharu, Nakamura, Shun
• Format: Article
• Language: English
• Subjects: Animals; Biological Sciences; Brain; Brain-Derived Neurotrophic Factor - deficiency; Brain-Derived Neurotrophic Factor - genetics; Brain-Derived Neurotrophic Factor - pharmacology; Brain-Derived Neurotrophic Factor - physiology; Calcium - physiology; Critical periods; Genotypes; Hippocampus - growth & development; Hippocampus - physiology; Knockout mice; Mice; Mice, Knockout; Neurology; Neurons; Neurons - physiology; Neuroscience; PDZ protein; PDZ proteins; Receptors; Receptors, AMPA - drug effects; Receptors, AMPA - physiology; Research grants; Somatosensory Cortex - growth & development; Somatosensory Cortex - physiology; Synapses; Synapses - physiology; Synaptic transmission; TrkB protein; Visual Cortex - growth & development; Visual Cortex - physiology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2131948100

Brain-derived neurotrophic factor (BDNF) is a critical modulator of central synaptic functions such as long-term potentiation in the hippocampal and visual cortex. Little is known, however, about its role in the development of excitatory glutamatergic synapses in vivo. We investigated the development of N-methyl-D-aspartate (NMDA) receptor (NMDAR)-only synapses (silent synapses) and found that silent synapses were prominent in acute thalamocortical brain slices from BDNF knockout mice even after the critical period. These synapses could be partially converted to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-containing ones by adding back BDNF alone to the slice or fully converted to together with electric stimulation without affecting NMDAR transmission. Electric stimulation alone was ineffective under the BDNF knockout background. Postsynaptically applied TrkB kinase inhibitor or calcium-chelating reagent blocked this conversion. Furthermore, the AMPAR C-terminal peptides essential for interaction with PDZ proteins postsynaptically prevented the unmasking of silent synapses. These results suggest that endogenous BDNF and neuronal activity synergistically activate AMPAR trafficking into synaptic sites.