PGE2 increases embryonic tail-flick in zebrafish at 28hpf. (A-C) Shows a 30-second movie representative of embryos from normal, vehicle and PGE2 at 28hpf. The frequency of the embryonic tail-flicks was observed from three replicates of group. No difference was observed in the frequency of embryonic tail-flick between the normal (movie 1A) and the vehicle (movie 1B). The embryonic tail-flick of the PGE2 (movie 1C) was observed to be more frequent than the vehicle.