Fig. 3.

Paired 300-ns pulses at the shortest interpulse intervals can cause larger [Ca²⁺]_i increase than a single 600-ns pulse. The experiments were performed in NG108 (A) and CHO cells (B and C). The field strength was 3.7 kV/cm (A and B) and 4.5 kV/cm (C). Individual panels show Ca²⁺ transients induced by single 300- and 600-ns pulses (left column) and by paired 300-ns pulses at the indicated interpulse intervals. Vertical dashed lines show when nsEP was applied. Graphs at the right display the peak amplitude of Ca²⁺ transient against the interpulse interval. For easier comparison, the peak amplitude of the transients evoked by a single 600-ns pulse is emphasized by shading. The asterisks show significantly higher effect of paired 300-ns pulses compared to a single 600-ns pulse (p < 0.05, one-tailed t-test). Mean ± s.e. for n ≥ 60.