Fig. 1.

Dose-response experiments identify 250 μM VPA as the maximum tolerated dose (MTD). Embryo survival (A) and hatching (B) were recorded daily from 0-7 dpf using concentrations of VPA ranging from 0-2000 μM. Treated embryos were continuously exposed to VPA from 6-120 hpf. 250 μM was found to be the MTD due to high embryo survival (A) and hatching (B). (C-D) Because zebrafish embryos are encased in a chorion until around 72 hpf, we wondered if VPA was not able to reach the embryos while they were in their chorion. As a result, we repeated the dose-response experiments in embryos where the chorion was punctured. We found no appreciable difference in survival or hatching in embryos with intact or punctured chorions, showing that we could treat the embryos during the early stages without having to remove the chorion. Experiments were repeated twice with 10 embryos per treatment each time.