Table 3

Effect of pH on agonist potency at P2X receptors

ReceptorpH 6.5pH 7.5pH 8.0
P2X2 3-a 1.3  ± 0.216.2  ± 1.428  ± 2
P2X3 3-b 2.1  ± 0.51.4  ± 0.31.4  ± 0.2
P2X2/3 3-c 1.8  ± 0.48.6  ± 1.28.3  ± 1.1

Agonist potency given in terms of EC50 value (μM) (mean ± S.E., n = 4–6) for the stated extracellular pH values.

  • ↵3-a Determined from slow responses to ATP at P2X2 receptors.

  • ↵3-b Determined from fast responses to ATP at P2X3receptors.

  • ↵3-c Determined from slow responses to α,β-meATP at P2X2/3 receptors.