Figure 2. Raw data illustrating that CO₂-evoked excitation of inspiratory neurones is blocked by the P2 receptor antagonist PPADS.

A and B, raw data illustrating the neuronal response to hypercapnia in the absence, and presence, of PPADS applied ionophoretically at the currents shown. C, response to L-glutamate in the presence of PPADS. D, response to L-glutamate in the presence of suramin (same neurone as in Fig. 1A). Vertical scale bars represent 100 μV.