Figure 2.

The close relationship between EPC decay time constant and MEPC decay time constant is lost after block of synaptic activity but is regained in solution containing low calcium. A, Scatter plot of EPC decay time constant versus MEPC decay time constant for control endplates (open circles) and endplates after block of activity with a TTX cuff (filled squares). EPC and MEPC recordings were obtained in Ringer’s solution containing normal extracellular calcium. There is marked prolongation of EPC decay time constant after blocking activity in endplates that had no prolongation of MEPC decay time constant. B, Scatter plot of EPC decay time constant versus MEPC decay time constant in Ringer’s solution containing low extracellular calcium for control endplates and endplates after block of activity with a TTX cuff. The data from endplates in which activity was blocked essentially overlaps data from control endplates. C, Superimposed EPCs recorded in solution containing low calcium from a control endplate (black) and an endplate in which synaptic activity was blocked by a TTX cuff for 8 d (gray). Although the peak amplitude of the EPC recorded in low calcium is larger after block of activity (Wang et al., 2004), there is little difference in the rate of EPC decay. Each EPC is preceded by a stimulus artifact (arrow). Note the difference in vertical scale relative to Figure 1A. D, The superimposed, normalized EPCs shown in C.