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GTP up‐regulated persistent Na + current and enhanced nociceptor excitability require Na V 1.9
Author(s) -
Östman Johan A. R.,
Nassar Mohammed A.,
Wood John N.,
Baker Mark 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.2007.147942
Subject(s) - sodium channel , biophysics , chemistry , gtp' , nociceptor , intracellular , sensory system , capsaicin , neuroscience , heterologous expression , nociception , electrophysiology , sensory neuron , microbiology and biotechnology , medicine , endocrinology , sodium , biology , biochemistry , receptor , gene , enzyme , organic chemistry , recombinant dna
Persistent tetrodotoxin‐resistant (TTX‐r) sodium currents up‐regulated by intracellular GTP have been invoked as the site of action of peripheral inflammatory mediators that lower pain thresholds, and ascribed to the Na V 1.9 sodium channel. Here we describe the properties of a global knock‐out of Na V 1.9 produced by replacing exons 4 and 5 in SCN11A with a neomycin resistance cassette, deleting the domain 1 voltage sensor and introducing a frameshift mutation. Recordings from small (< 25 μm apparent diameter) sensory neurones indicated that channel loss eliminates a TTX‐r persistent current. Intracellular dialysis of GTP‐γ‐S did not cause an up‐regulation of persistent Na + current in Na V 1.9‐null neurones and the concomitant negative shift in voltage‐threshold seen in wild‐type and heterozygous neurones. Heterologous hNa V 1.9 expression in Na V 1.9 knock‐out sensory neurones confirms that the human clone can restore the persistent Na + current. Taken together, these findings demonstrate that Na V 1.9 underlies the G‐protein pathway‐regulated TTX‐r persistent Na + current in small diameter sensory neurones that may drive spontaneous discharge in nociceptive nerve fibres during inflammation.