Tetanic stimulation (50 Hz, 1 min) by either conventional pulses or nsPEF does not change the nerve refractoriness. (a) The timeline and CAP traces from a representative experiment. Before and after each tetanus, CAPs were evoked by paired stimuli with interpulse intervals of 1, 1.5, 2, 3, and 4 ms. The tetani consisted of 3,000 single stimuli, either nsPEF (8 kV, 6.4 kV/cm) or conventional (2–4 V, 206–412 V/m), delivered with 50-ms intervals (1 min total). Shown in panels 2 and 4 are CAPs evoked by the first and the last stimuli in each tetanus (the latter CAP is smaller). See text for more details. (b) The inhibition of the test CAPs as a function of the interpulse interval, before and after tetani (open and filled symbols, respectively). The amplitude of the conditioning CAP is taken as 100%. Mean +/− s.e., n = 8 for all groups. For clarity, error bars are shown in one direction only.