A) As previously reported [14], BNST lesions reduce 10% CO2-evoked freezing. However, BNST lesions do not elicit 10% CO2-evoked jumping. ANOVA revealed an interaction between CO2 concentration and lesion status (F(1,49) = 7.56, p = 0.0083, n = 15, 9, 18, 11). Planned contrast testing revealed that BNST-lesioned mice freeze less than sham-lesioned mice in 10% CO2 (**p = 0.0032). However, ANOVA revealed no effect of CO2 concentration on jumping (F(1,49) = 1.4, p = 0.2425), no effect of lesion (F(1,49) = 2.797, p = 0.1008), and no interaction (F(1,49) = 1.4, p = 0.2425). B) Hippocampus lesions do not alter 10% CO2-evoked freezing behavior or elicit 10% CO2-evoked jumping. ANOVA revealed an effect of CO2 concentration on freezing (F(1,43) = 253.2, p < 0.0001, n = 15, 7, 18, 7), but no effect of lesion (F(1,43) = 0.0439, p = 0.8350), and no interaction (F(1,43) = 0.5889, p = 0.5889). ANOVA revealed no effect of CO2 on jumping (F(1,43) = 3.14, p = 0.0835), no effect of lesion (F(1,43) = 0.004056, p = 9495), and no interaction (F(1,43) = 0.06299, p = 0.8030).