Obaid A L, Orkand R K, Gainer H, Salzberg B M
J Gen Physiol. 1985 Apr;85(4):481-9. doi: 10.1085/jgp.85.4.481.
Voltage-sensitive dyes were used to record by optical means membrane potential changes from nerve terminals in the isolated frog neurohypophysis. Following the block of voltage-sensitive Na+ channels by tetrodotoxin (TTX) and K+ channels by tetraethylammonium (TEA), direct electric field stimulation of the nerve terminals still evoked large active responses. These responses were reversibly blocked by the addition of 0.5 mM CdCl2. At both normal and low [Na+]o, the regenerative response appeared to increase with increasing [Ca++]o (0.1-10 mM). There was a marked decrease in the size of the response, as well as in its rate of rise, at low [Ca++]o (0.2 mM) when [Na+]o was reduced from 120 to 8 mM (replaced by sucrose), but little if any effect of this reduction of [Na+]o at normal [Ca++]o. In normal [Ca++]o, these local responses most probably arise from an inward Ca++ current associated with hormone release from these nerve terminals. At low [Ca++]o, Na+ appears to contribute to the TTX-insensitive inward current.
使用电压敏感染料通过光学手段记录离体青蛙神经垂体中神经末梢的膜电位变化。在用河豚毒素（TTX）阻断电压敏感的Na⁺通道和用四乙铵（TEA）阻断K⁺通道后，直接电场刺激神经末梢仍能诱发大的主动反应。加入0.5 mM CdCl₂可使这些反应可逆性阻断。在正常和低[Na⁺]ₒ条件下，再生反应似乎随[Ca²⁺]ₒ（0.1 - 10 mM）的增加而增强。当[Na⁺]ₒ从120 mM降至8 mM（用蔗糖替代）时，在低[Ca²⁺]ₒ（0.2 mM）条件下，反应的大小及其上升速率均显著降低，但在正常[Ca²⁺]ₒ条件下，[Na⁺]ₒ的这种降低几乎没有影响。在正常[Ca²⁺]ₒ条件下，这些局部反应很可能源于与这些神经末梢激素释放相关的内向Ca²⁺电流。在低[Ca²⁺]ₒ条件下，Na⁺似乎对TTX不敏感的内向电流有贡献。
