PLC is required for the fast block. (A and B) Representative fertilization recordings made in 1 µM U73122 (A) or 1 µM U73343 (B). Dashed line denotes 0 mV, and arrows indicate sperm additions. (C–E) Tukey box plot distributions of the resting (C) and fertilization (D) potentials and the depolarization rates (E) made in indicated treatments (n = 7–8, recorded over 3–5 experiment days per treatment, the mean values ± SEM are reported). The gray lines behind the box plots represent the Tukey box plot distributions for the control (MR/5) data, where the solid line represents the median value and the dashed lines denote the data spread from 25 and 75% and the whiskers reflect 10–90%. (F) Percent polyspermic embryos out of total developed embryos in control (MR/5), U73122, and U73343. *, P < 0.05; **, P < 0.01.