Data from: Development of resurgent and persistent sodium currents in mesencephalic trigeminal neurons

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 (INaR and INaP, 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 INaR and INaP 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 0-6 neurons to postnatal day 7-14 neurons. Although these neurons do not exhibit subthreshold oscillations or burst discharges with high-frequency firing, INaR and INaP do exist in Mes V neurons at postnatal day 0-6. When the spike frequency at rheobase was examined in firing Mes V neurons, the developmental change in firing frequency among P7 to P14 neurons was significant. INaR and INaP density at −40 mV also increased significantly among P7 to P14 neurons.
The change to an increase in excitability in the P7-14 group could result from this quantitative change in INaP. In neurons older than P7 that exhibit repetitive firing, quantitative increases in INaR and INaP density may be major factors that facilitate and promote high-frequency firing as a function of age in Mes V neurons.

钠通道在三叉神经中脑核（mesencephalic trigeminal, Mes V）神经元及其他神经系统的神经膜特性形成中发挥多重作用。三叉神经中脑核神经元可呈现条件性强高频锋电位爆发。既往研究表明，复活型钠电流（resurgent sodium current, INaR）与持续性钠电流（persistent sodium current, INaP）可在阈下电位下产生微弱电流，参与锋电位的触发。此类电流在维持及实现爆发性高频锋电位发放过程中发挥重要作用。
本研究针对三叉神经中脑核神经元中介导高频锋电位发放的河豚毒素敏感型INaR与INaP的发育变化展开探究。全细胞膜片钳记录结果显示，从出生后0~6天神经元到出生后7~14天神经元，两种电流的密度均提升1.5倍。尽管出生后0~6天的三叉神经中脑核神经元未表现出阈下振荡或高频爆发放电，但此时已存在INaR与INaP。对处于基强度放电状态的三叉神经中脑核神经元的锋电位频率进行检测后发现，出生后7~14天神经元的放电频率存在显著的发育性变化；同时，-40 mV电位下的INaR与INaP密度在该阶段同样显著升高。
出生后7~14天组神经元兴奋性的提升，可能源于INaP的上述量化变化。对于出生后7天以上表现出重复放电的神经元而言，INaR与INaP密度的量化提升，或为随年龄增长促进三叉神经中脑核神经元高频放电的主要因素。