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Development of resurgent and persistent sodium currents in mesencephalic trigeminal neurons
Author(s) -
Enomoto Akifumi,
Seki Soju,
Tanaka Susumu,
Ishihama Kohji,
Yamanishi Tadashi,
Kogo Mikihiko,
Hamada Suguru
Publication year - 2018
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.24134
Subject(s) - nap , rheobase , tetrodotoxin , neuroscience , bursting , sodium channel , subthreshold conduction , patch clamp , chemistry , neuron , membrane potential , biophysics , electrophysiology , biology , sodium , physics , voltage , organic chemistry , transistor , quantum mechanics
Sodium channels play multiple roles in the formation of neural membrane properties in mesencephalic trigeminal (Mes V) neurons and in other neural systems. Mes V neurons exhibit conditional robust high‐frequency spike discharges. As previously reported, resurgent and persistent sodium currents ( I NaR and I NaP , respectively) may carry small currents at subthreshold voltages that contribute to generation of spike firing. These currents play an important role in maintaining and allowing high‐frequency spike discharge during a burst. In the present study, we investigated the developmental changes in tetrodotoxin‐sensitive I NaR and I NaP underlying high‐frequency spike discharges in Mes V neurons. Whole‐cell patch‐clamp recordings showed that both current densities increased one and a half times from postnatal day (P) 0–6 neurons to P7–14 neurons. Although these neurons do not exhibit subthreshold oscillations or burst discharges with high‐frequency firing, I NaR and I NaP do exist in Mes V neurons at P0–6. When the spike frequency at rheobase was examined in firing Mes V neurons, the developmental change in firing frequency among P7–14 neurons was significant. I NaR and I NaP density at −40 mV also increased significantly among P7–14 neurons. The change to an increase in excitability in the P7–14 group could result from this quantitative change in I NaP. In neurons older than P7 that exhibit repetitive firing, quantitative increases in I NaR and I NaP density may be major factors that facilitate and promote high‐frequency firing as a function of age in Mes V neurons.