Bossu J L, Feltz A
Neurosci Lett. 1984 Oct 12;51(2):241-6. doi: 10.1016/0304-3940(84)90558-5.
Conditions were devised to isolate in cranial sensory neurones transfer of Na ions: K and Ca were omitted from the extracellular medium, and simultaneously cells were intracellularly loaded with 120 mM caesium and 20 mM TEA at [Ca]i = 10(-8) M. A tetrodotoxin (TTX)-resistant current was shown to be elicited by step depolarization from -25 MV upwards. This current successively activates and inactivates at increasing rates on further depolarization and at 0 mV (where peak amplitude is reached) its time course is of 20-50 ms. Absence of TTX-sensitivity (up to 15 microM), slow time course and an activation curve shifted by 15 mV towards the depolarized potentials differentiate this current from the more classical fast Na current which can be elicited on the same cells. Inactivation was provoked by a prepulse of varying amplitude and duration: with a prepulse command to -20 mV, inactivation was of 50% within a delay of 300 ms and almost 100% in about 1 min. After complete inactivation by command to 0 mV for 300 ms, recovery by holding the potential at -80 mV was of 50% in 205 ms, and of 100% after 1-4 s. It is concluded that a charge transfer of Na accounts for most of the hump which prolongs the action potential of these sensory neurones, and thus it can be proposed that spike duration as modulated by neurotransmitters may also involve Na in addition to Ca.
细胞外培养基中省略钾离子和钙离子，同时在细胞内加载120 mM铯离子和20 mM四乙铵，细胞内钙离子浓度为10^(-8) M。从-25 mV向上的阶跃去极化可引发一种对河豚毒素（TTX）不敏感的电流。该电流在进一步去极化时以不断增加的速率相继激活和失活，在0 mV（达到峰值幅度处）时其时间进程为20 - 50 ms。缺乏TTX敏感性（高达15 μM）、缓慢的时间进程以及激活曲线向去极化电位方向偏移15 mV，使得这种电流与在同一细胞上可引发的更经典的快速钠离子电流区分开来。通过不同幅度和持续时间的预脉冲引发失活：当预脉冲指令为-20 mV时，在300 ms的延迟内失活率为50%，在约1分钟内几乎达到100%。在通过指令至0 mV持续300 ms完全失活后，将电位保持在-80 mV时，205 ms内恢复率为50%，1 - 4 s后恢复率为100%。结论是，钠离子的电荷转移构成了延长这些感觉神经元动作电位的大部分驼峰，因此可以提出，除了钙离子外，神经递质调节的动作电位持续时间可能也涉及钠离子。
