Fig. 1

Treatment of embryos and larvae with the GABA pathway inhibitor pentylenetetrazole induces convulsions that are characterised by increased locomotor activity and calcium influx into muscle cells. (A) 4 dpf larvae were exposed to 1.25, 2.5, 5, 10, 20, 40 or 80 mM PTZ for 10 minutes, then movements were recorded over the next 10 minutes. Values are given as means (n=4); error bars indicate s.e.m. ***Significantly different (P<0.001) from untreated embryos, using one-way ANOVA with Dunnett’s post-test. Representative traces of movements after exposure to each PTZ concentration lie beneath each corresponding value for PTZ concentration in the histogram. Black, green and red traces indicate swimming speeds of 0–1.5, 1.5–6 and >6 mm/second, respectively. (B) In situ hybridisation analysis reveals strong expression of GABA_A receptor component genes gabra1 and gabrg2 throughout the brain of 50 hpf embryos. (C) Induction of convulsions in embryos by exposure to PTZ. Panel 1: representative traces of locomotor activity of 48 hpf embryos untreated (PTZ) and exposed to 20 mM PTZ (+PTZ). Black, green and red traces indicate swimming speeds of 0–1.5, 1.5–6 and >6 mm/second, respectively. Panels 2, 3 and 4: live confocal imaging of GCaMP-3 fluorescence in the muscle of a 50 hpf zebrafish embryo transiently expressing a mylz2:GCaMP3 reporter transgene. Images are taken from a movie after 5 minutes of exposure to 20 mM PTZ, before (Panel 2), during (Panel 3) and after (Panel 4) a single convulsion. Panel 5: graph of GCaMP-3 fluorescence from the embryo in Panels 2–4, over a period in which two consecutive convulsions occurred.