Fig. 9. (A ) Step depolarizations (100 mV) were applied as a train with the characteristics described in the top component of the figure. In the lower traces, the first and last events in the train are virtually superimposable, even in the presence of 10 μm cOA. (B ) Compounded data from five replicated experiments confirm that no frequency-dependent cumulative block is apparent in the presence of cOA.