Gigantic spontaneous events vanish in response to diminished Ca²⁺, buffered Ca²⁺, or blocked Na_V.

<p><b>(A)</b> Box and whisker plot of mEPSP amplitudes at 0.2 mM extracellular Ca²⁺. Plot as in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007577#pgen.1007577.g005" target="_blank">Fig 5</a> (*** <i>p</i> < 0.001 by Kruskal-Wallis ANOVA with Dunn’s post-hoc vs. either <i>w</i>^<i>1118</i> or WT; <i>n</i> > 780 mEPSPs for each genotype). <b>(B)</b> Cumulative probability histogram of the data in (A) showing a rightward shift in mEPSP amplitudes for SL- and RQ,SL-expressing NMJs– but less so than for 0.5 mM Ca²⁺, with smaller and fewer gigantic events (compare to <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007577#pgen.1007577.g005" target="_blank">Fig 5</a>). <b>(C)</b> Box and whisker plots demonstrating elimination of gigantic spontaneous events by various manipulations. (*** <i>p</i> < 0.001 by Fisher’s exact test examining the incidence of gigantic mEPSPs > 10 mV vs. RQ,SL or SL alone, as appropriate). <b>(D-F)</b> Cumulative probability histograms of mEPSP size separately showing the effects of zero extracellular Ca²⁺ (D); application of BAPTA-AM in 0.5 mM Ca²⁺ (E); application of TTX in 0.5 mM Ca²⁺ (F). In each case, the rightward shift in mEPSP size distribution persists due to RQ,SL expression. However, the gigantic spontaneous events are eliminated (see frequency shift at arrowheads). <b>(G)</b> Box and whisker plot of spontaneous event amplitudes at 0.5 mM extracellular Ca²⁺ + TTX, with an intact central nervous system. (*** <i>p</i> < 0.001 by Mann-Whitney U Test of WT vs. RQ,SL; <i>n</i> = 900 mEPSPs for each genotype). <b>(H)</b> Cumulative probability histogram of the data in (G).