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Brain‐derived neurotrophic factor enhances the excitability of rat sensory neurons through activation of the p75 neurotrophin receptor and the sphingomyelin pathway
Author(s) -
Zhang Y. H.,
Chi Xian Xuan,
Nicol G. D.
Publication year - 2008
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2008.152439
Subject(s) - neurotrophin , tropomyosin receptor kinase b , low affinity nerve growth factor receptor , nerve growth factor , tropomyosin receptor kinase a , brain derived neurotrophic factor , neuroscience , trk receptor , neurotrophic factors , chemistry , sphingosine kinase , tropomyosin receptor kinase c , microbiology and biotechnology , receptor , biology , sphingosine , platelet derived growth factor receptor , sphingosine 1 phosphate , growth factor , biochemistry
Neurotrophin‐mediated signalling cascades can be initiated by activation of either the p75 neurotrophin receptor (p75 NTR ) or the more selective tyrosine kinase receptors. Previously, we demonstrated that nerve growth factor (NGF) increased the excitability of sensory neurons through activation of p75 NTR to liberate sphingosine 1‐phosphate. If neurotrophins can modulate the excitability of small diameter sensory neurons through activation of p75 NTR , then brain‐derived neurotrophic factor (BDNF) should produce the same sensitizing action as did NGF. In this report, we show that focally applied BDNF increases the number of action potentials (APs) evoked by a ramp of depolarizing current by reducing the rheobase without altering the firing threshold. This increased excitability results, in part, from the capacity of BDNF to enhance a tetrodotoxin‐resistant sodium current (TTX‐R I Na ) and to suppress a delayed rectifier‐like potassium current ( I K ). The idea that BDNF acts via p75 NTR is supported by the following observations. The sensitizing action of BDNF is prevented by pretreatment with a blocking antibody to p75 NTR or an inhibitor of sphingosine kinase (dimethylsphingosine), but not by inhibitors of tyrosine kinase receptors (K252a or AG879). Furthermore, using single‐cell RT‐PCR, neurons that were sensitized by BDNF expressed the mRNA for p75 NTR but not TrkB. These results demonstrate that neurotrophins can modulate the excitability of small diameter capsaicin‐sensitive sensory neurons through the activation of p75 NTR and its downstream sphingomyelin signalling cascade. Neurotrophins released upon activation of a variety of immuno‐competent cells may be important mediators that give rise to the enhanced neuronal sensitivity associated with the inflammatory response.