Figure 1. HCO₃ ⁻‐dependent modulation of chemosensitive RTN neurons.

A, trace of firing rate and segments of holding current shows a typical response of an RTN neuron in a slice incubated in normal Ringer's solution containing 26 mM HCO₃ ⁻ to an increase in CO₂ from 5% to 10%. After returning to control conditions, exposure to HCO₃ ⁻‐free Hepes buffer (pH 7.3) strongly inhibited baseline activity. B, summary data (n = 18) show average firing rate under control conditions and during exposure to HCO₃ ⁻‐free Hepes buffer (pH_o 7.3) and 10% CO₂ (pH_o 7.0). C, trace of firing rate and segments of holding current from a chemosensitive RTN neuron shows that exposure to isohydric HCO₃ ⁻ (10% CO₂/52 mM HCO₃ ⁻) caused a robust increase in activity. D, summary data (n = 19) show average firing rate of chemosensitive RTN neurons under control conditions and during exposure to isohydric HCO₃ ⁻ and 10% CO₂ (pH_o 7.0). E, trace of firing rate and segments of holding current from a CO₂/H⁺‐insensitive RTN neuron shows that exposure to isohydric HCO₃ ⁻ (10% CO₂/52 mM HCO₃ ⁻) minimally affected firing behaviour. F, summary data (n = 10) show average firing activity of CO₂/H⁺‐insensitive RTN neurons under control conditions and during exposure to isohydric HCO₃ ⁻ and 10% CO₂ (pH_o 7.0). One‐way ANOVA with Tukey multiple comparison test. ^**** P < 0.0001. [Color figure can be viewed at http://wileyonlinelibrary.com]