Figure 5. Acidosis-stimulated raphe neurones responded to changes in pH in the absence of CO₂ and bicarbonate.

This neurone increased its firing rate in response to hypercapnic acidosis, and also responded to changes in pH in Hepes-buffered solution. When switching between normal Ringer solution (pH 7.4, P_CO2 5 %) and Hepes-buffered solution (pH 7.4, P_CO2 0 %), the neurone responded as other acidosis-stimulated neurones did to isohydric hypocapnia. Bars at bottom depict the presence or absence of Hepes, CO₂ and bicarbonate.