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.
Department of Zoology, Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
Daniela B
DB
Pereira
Nelson
N
Rebola
Ricardo J
RJ
Rodrigues
Rodrigo A
RA
Cunha
Arsélio P
AP
Carvalho
Carlos B
CB
Duarte
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