Presynaptic OSN GABA receptors accelerate behavioral responses to odor pulse termination. Presynaptic OSN GABA receptors accelerate behavioral responses to odor pulse termination. A, B, Behavioral responses of flies within 3 cm from the odor port show avoidance during and after a 1 s Eb pulse of 1:5 (A) and 1:1 (B). Mean ± SEM; n = 100–200 total flies per genotype and concentration assayed over at least 10 independent experiments. C, Average velocity of flies within 3 cm from the odor port during and after a 1 s 1:5 Eb pulse. During and immediately after the odor pulse, the velocity away from the odor port is significantly increased by individual knockdown of GABAA receptors and simultaneous knockdown of GABAA and GABAB receptors. The velocity between 2 and 4 s after the odor pulse is significantly increased by simultaneous knockdown of GABAA and GABAB receptors. Statistical analysis: two-way ANOVA with Bonferroni post hoc test (asterisks are color coded to indicate pairwise comparisons vs control), *p < 0.05; **p < 0.01. D, Average velocity during 1:1 Eb odor pulses is unaffected by the knockdown of GABA receptors. However, simultaneous knockdown of GABAA and GABAB receptors significantly prolongs avoidance between 1 and 4 s after termination of the odor pulse. Statistical analysis: two-way ANOVA with Bonferroni post hoc test, *p < 0.05; **p < 0.01. E, F, Average velocity of flies that are >3 cm away from the odor port is unaffected by knockdown of GABA receptors for 1:5 (E) 1:1 (F) Eb odor pulses. Mean ± SEM. N = 200–300 flies. Davide Raccuglia et al. eNeuro 2016;3:ENEURO.0080-16.2016 ©2016 by Society for Neuroscience