(a) Original trace showing the effect of pyridoxalphosphate-6-azophenyl-2′,5′-disulphonic acid (100 μM) on responses to adenosine 5′-triphosphate (ATP; •; 1–30 μM) in longitudinal strips of rat gastric fundus. Magnitude of (b) relaxant responses and (c) contractile responses to ATP (1–30 μM) in longitudinal strips of rat gastric fundus in the absence (control) and presence of pyridoxalphosphate-6-azophenyl-2′,5′-disulphonic acid (PPADS; 100 μM), apamin (1 μM) or desensitization to α,β-methylene adenosine 5′-triphosphate (10 μM, three additions). Values are means±s.e.mean for 4–5 experiments. *Significant difference from control (P<0.05, two-way MANOVA followed by Student-Newman-Keuls test).