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Specific distribution of sodium channels in axons of rat embryo spinal motoneurones
Author(s) -
AlessandriHaber Nicole,
Paillart Christophe,
Arsac Christine,
Gola Maurice,
Couraud François,
Crest Marcel
Publication year - 1999
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 - 10.1111/j.1469-7793.1999.0203r.x
Subject(s) - neurite , soma , antidromic , sodium channel , axon , neuroscience , electrophysiology , chemistry , biophysics , microbiology and biotechnology , anatomy , biology , sodium , in vitro , biochemistry , organic chemistry
1 The distribution of Na + channels and development of excitability were investigated in vitro in purified spinal motoneurones obtained from rat embryos at E14, using electrophysiological, immunocytochemical and autoradiographical methods. 2 One hour after plating the motoneurones (DIV0), only somas were present. They expressed a robust delayed rectifier K + current ( I DR ) and a fast‐inactivating A‐type K + current ( I A ). The rapid neuritic outgrowth was paralleled by the emergence of a fast‐activating TTX‐sensitive sodium current ( I Na ), and by an increase in both K + currents. 3 The change in the three currents was measured daily, up to DIV8. The large increase in I Na observed after DIV2 was accompanied by the onset of excitability. Spontaneous activity was observed as from DIV6. 4 The occurrence of axonal differentiation was confirmed by the fact that (i) only one neurite per motoneurone generated antidromic action potentials; and (ii) 125 I‐α‐scorpion toxin binding, a specific marker of Na + channels, labelled only one neurite and the greatest density was observed in the initial segment. Na + channels therefore selectively targeted the axon and were absent from the dendrites and somas. 5 The specific distribution of Na + channels was detectable as soon as the neurites began to grow. When the neuritic outgrowth was blocked by nocodazole, no I Na developed. 6 It was concluded that, in spinal embryonic motoneurone in cell culture, Na + channels, the expression of which starts with neuritic differentiation, are selectively addressed to the axonal process, whereas K + channels are present in the soma prior to the neuritic outgrowth.