Fig. 1

GABAergic tone that controls respiratory burst frequency strongly decreases following hibernation. Integrated vagus nerve activity (CN X) was rhythmic in fully intact brainstem preparations (top right box) from control and hibernated animals. A Top, continuous recording of CNX during perfusion of increasing doses of bicuculline in a control preparation (black). Bottom, zoomed in view of epochs (orange boxes) indicated in continuous trace directly above. In control preparations, bath application of bicuculline led to a dose dependent decrease in respiratory burst frequency and dose-dependent increase in non-respiratory burst frequency. B Top, continuous recording of CNX during perfusion of increasing doses of bicuculline in a preparation from a hibernated animal (blue). Bottom, zoomed in view of epochs (orange boxes) indicated in continuous trace above. Respiratory output from hibernated preparations was insensitive to systemic application of bicuculline, however non-respiratory motor bursting increased in a dose-dependent manner like controls. C Summary of bicuculline-mediated changes in respiratory burst frequency. There was a significant interaction between drug and group by two-way ANOVA (F_(4,32) = 6.741; p = 0.0005). Additionally, at 10 µM bicuculline, respiratory burst frequency from controls was significantly lower than hibernated preparations by Holm-Sidak’s post-hoc test (p = 0.0111; n = 5/group). D Summary of bicuculline-mediated changes in non-respiratory burst frequency. Bicuculline mediated similar increases in non-respiratory bursting in control and hibernated groups. There was no significant interaction between drug and group by two-way ANOVA (F_(4,32) = 0.7948; p = 0.5373; n = 5/group). a.u., arbitrary units. In summary plots, thick lines represent the group average and thin lines are responses of individual preparations