Figure 4.
Activation of chemoreceptor afferent fibers by ATP. A, Effects of ATP (1 and 3 mm, 0.3 ml) on the sinus nerve activity. Note that a short period of inhibition after the initial burst of discharge was seen in the afferent units with larger spikes. B, The P2 receptor antagonist PPADS (30 μm) reversibly blocks the effects of ATP.