Kuba K, Nishi S
Pflugers Arch. 1979 Jan 31;378(3):205-12. doi: 10.1007/BF00592737.
The membrane current underlying the fast excitatory postsynaptic potential (EPSC) of bullfrog sympathetic ganglion cells was studied. The relationship between the EPSC amplitude and membrane potential was linear at negative levels of membrane potential, but deviated from the linearity toward a smaller amplitude at positive levels. The falling phase of EPSC almost followed a single exponential decay. The half-decay time (HDT) of EPSC's increased exponentially with an increase in the negativity of membrane potential. The rise time (RT) was also prolonged slightly with membrane hyperpolarization. Lowering of temperature decreased the EPSC amplitude, lengthened markedly the HDT and increased the slope relating the logarithm of the HDT to membrane potential. Neostigmine (1 x 10(-5) M) prolonged both the RT and HDT. A decrease in Ca2+ concentration caused a marked reduction in the EPSC amplitude, and a slight shortening in the RT and HDT. An increase in Ca2+ concentration significantly prolonged the RT and HDT without altering the slope of the relationship between the HDT and membrane potential, while the amplitude of EPSC was increased slightly. The HDT was independent of EPSC amplitude. It is suggested that the mechanism responsible for closing the ion channels of the nicotinic receptor at the subsynaptic membrane is regulated by membrane potential. The possible mechanisms of the action of Ca2+ on the decay phase of EPSC were discussed.
对牛蛙交感神经节细胞快速兴奋性突触后电位（EPSC）的膜电流进行了研究。在膜电位为负时，EPSC幅度与膜电位之间呈线性关系，但在膜电位为正时，该关系偏离线性，幅度变小。EPSC的下降相几乎呈单指数衰减。EPSC的半衰期（HDT）随着膜电位负值的增加呈指数增加。上升时间（RT）也随着膜超极化而略有延长。降低温度会降低EPSC幅度，显著延长HDT，并增加HDT对数与膜电位之间关系的斜率。新斯的明（1×10⁻⁵ M）会延长RT和HDT。Ca²⁺浓度降低会导致EPSC幅度显著降低，RT和HDT略有缩短。Ca²⁺浓度增加会显著延长RT和HDT，但不改变HDT与膜电位之间关系的斜率，而EPSC幅度略有增加。HDT与EPSC幅度无关。提示突触后膜烟碱样受体离子通道关闭的机制受膜电位调节。讨论了Ca²⁺对EPSC衰减相作用的可能机制。
