Mauthner neuron in auts2a mutants have reduced excitability. A, Schematic of experimental set up. Calcium activity in the Mauthner neuron was observed on antidromic stimulation. Mauthner neuron was retrogradely labeled with OGB-1 dextran. B, ΔF/F profile for an example wild-type (WT) larva on antidromic stimulation with 10-μA (left) and 20-μA (right) stimulus intensity. Mauthner neuron fired reliably at the threshold intensity of 20 μA. C, Representative raster plot from a wild-type larva (left) and mutant larva (right). Each row represents average ΔF/F over five trials at the respective stimulus intensity. The threshold for calcium activity for wild-type larva is 20 μA, whereas for the mutant larva is 70 μA. D, Normalized histogram of calcium activity threshold for wild type (n = 9 larvae) and auts2a mutants (n = 12 larvae). E, Summary data of probability of calcium activity at 0.5×, 1×, 1.5× threshold stimulus intensity for wild-type and mutant group. F, ΔF/F profiles for a representative wild-type larva (black) and a mutant larva (red) on antidromic stimulation. Shaded regions represent SEM from five trials. G, Summary data of peak calcium signal in wild type (n = 45 trials, 9 larvae) and auts2a mutants (n = 60 trials, 12 larvae); *p < 0.05, ***p < 0.0005; ns: not significant; Mann–Whitney U test. H, Calcium activity threshold for wild-type (n = 9) and mutant (n = 7) larvae before and after bath application of 50 μm strychnine and 100 μm gabazine. Mauthner neurons were labeled with calcium green dextran for this experiment. Wilcoxon signed-rank test. I, Peak ΔF/F for wild-type (n = 9) and mutant (n = 7) larvae before and after bath application of 50 μm strychnine and 100 μm gabazine. Paired sample t test.
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