Fig. 2

Hibernation decreases sensitivity to GABA_AR agonist (muscimol)-mediated respiratory frequency decline. Integrated vagus nerve activity (CN X) was rhythmic in fully intact brainstem preparations (top left box) from control and hibernated animals. A Continuous recording of CNX during perfusion of increasing doses of muscimol in a control preparation (black). In control preparations, respiratory output was unchanged by bath application of 500 nM muscimol but decreased following elevation to 1 µM muscimol and ultimately stopped following further elevation to 3 µM muscimol. Preparations were recovered by exposure to bicuculine, demonstrating specificity of the GABA_A receptor agonist. B Continuous recording of CNX during perfusion of increasing doses of muscimol in a preparation from a hibernated animal (blue). Preparations from hibernated animals were relatively insensitive to muscimol mediated changes in respiratory burst frequency compared to controls. C Summary of muscimol-mediated changes in respiratory burst frequency. There was a significant interaction between drug and group by two-way ANOVA(F_(3,24) = 4.045; p = 0.0184). Additionally, at 1 µM muscimol, respiratory burst frequency from controls was significantly lower than hibernated preparations by Holm-Šidák’s post-hoc test (p = 0.0007, n = 5/group). D Summary of muscimol-mediated changes in respiratory burst frequency relative to baseline. There was a significant interaction between drug and group by two-way ANOVA(F_(3,24) = 7.184; p = 0.0013). Additionally, at 1 µM muscimol, respiratory burst frequency from controls was significantly lower than hibernated preparations relative to baseline by Holm-Sidak’s post-hoc test (p = 0.0030, n = 5 per group). In summary plots, thick lines represent the group average and thin lines are individual preparations