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  • Title: BDNF down-regulates neurotrophin responsiveness, TrkB protein and TrkB mRNA levels in cultured rat hippocampal neurons.
    Author: Frank L, Ventimiglia R, Anderson K, Lindsay RM, Rudge JS.
    Journal: Eur J Neurosci; 1996 Jun; 8(6):1220-30. PubMed ID: 8752592.
    Abstract:
    Regulation of Trk receptors by their ligands, the neurotrophins, was investigated in dissociated cultures of embryonic day 18 rat hippocampal neurons. Cultures were exposed to brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) or NT-4/5 for 24 h upon plating followed by factor washout. As determined by immunohistochemical staining and phosphotyrosine blotting, the functional responses to acute stimulation with BDNF, NT-3 and NT-4/5, including c-Fos induction and phosphorylation of Trk and extracellular signal-regulated kinase (ERK) proteins, were significantly decreased after 6 days in culture by prior exposure to BDNF. As determined by Western and Northern blot analysis respectively, there was a parallel down-regulation of TrkB protein as well as of trkB and trkC mRNA levels in BDNF-pretreated cultures. Exposure to NT-3 or NT-4/5 at the same concentrations as BDNF did not down-regulate any of the measured cellular responses or TrkB protein and/or trkB and trkC mRNA levels. Regulation of hippocampal neuronal Trkb protein does not appear to be just a development phenomenon, as infusion of BDNF into the hippocampus of adult rats for 6 days produced an 80% decrease in levels of full-length TrkB protein. We thus show that exposure of hippocampal neurons to BDNF, both in culture and in the adult brain, results in down-regulation of TrkB. At least in vitro, this leads to long-term functional desensitization to BDNF, NT-3 and NT-4/5, as well as down-regulation of trkB and trkC mRNA.
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