Trkb receptors modulation of glutamate release is limited to a subset of nerve terminals in the adult rat hippocampus.
Brain-derived neurotrophic factor (BDNF) modulates glutamatergic excitatory transmission in hippocampal primary cultures by acting at a presynaptic locus. Although it has been suggested that BDNF also modulates adult hippocampus glutamatergic transmission, this remains a matter of controversy. To clarify a putative role for this neurotrophin in the modulation of glutamate release we applied exogenous BDNF to isolated adult rat hippocampal nerve terminals. BDNF, at 100 ng/ml, potentiated by 25% the K(+)-evoked release of [(3)H]glutamate from hippocampal synaptosomes. The small effect of BDNF on [(3)H]glutamate release correlated with a modest increase in phospholipase Cgamma (PLCgamma) phosphorylation, and with the lack of effect of BDNF on extracellular-signal regulated kinase (ERK) and Akt phosphorylation. Immunocytochemistry studies demonstrated that only about one-third of glutamatergic synaptosomes were positive for TrkB immunoreactivity. Furthermore, biotinylation and subsynaptic fractionation studies showed that only one-fourth of total full-length TrkB was present at the plasma membrane, evenly distributed between the presynaptic active zone and the postsynaptic density. These results indicate that BDNF modulates synaptic transmission presynaptically in a small subset of hippocampal glutamatergic synapses that contain TrkB and that express the receptor on the plasma membrane.
Pereira
Daniela B
DB
Department of Zoology, Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
Rebola
Nelson
N
Rodrigues
Ricardo J
RJ
Cunha
Rodrigo A
RA
Carvalho
Arsélio P
AP
Duarte
Carlos B
CB
D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020813:Receptor, trkB / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
D019208:Brain-Derived Neurotrophic Factor; D018698:Glutamic Acid; D020813:Receptor, trkB; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases