Fig. 3.

ATP release during CO₂ chemosensory transduction. a Schematic of the ventral surface of the medulla oblongata showing sites of in vivo ATP release (black circles) and no ATP release (open circles) relative to known landmarks and major blood vessels (7n 7th nucleus, XII XIIth nerve, py pyramids) in an anaesthetized, ventilated rat. Sample records of ATP release (Net ATP) for different locations shown on the right in combination with end-tidal CO₂ and integrated phrenic nerve activity (PNG). Reproduced with permission from [49]. b In vitro recordings of ATP release, measured from the caudal location near to the XIIth nerve, evoked by changes in PCO₂ at constant extracellular pH. Note that a reduction of PCO₂ from an initial level of 35 mmHg causes a drop in ATP release at the surface of the medulla and that there is a resting ATP tone, visible when the sensors are removed from the surface of the medulla at the end of the recording (top trace, dotted lines). Reproduced with permission from [15]