Whole-cell patch clamp recordings were used to characterise the physiological and pharmacological properties of P2X receptors of mouse and guinea pig myenteric neurons from the small intestine. ATP application induced a rapid inward current in 95% of recorded neurons of both species when were voltage clamped at −60mV. Concentration–response curves for ATP (1–3000µM) yielded EC 50 values of 114 and 115μM for mouse and guinea pig myenteric neurons, respectively, with a Hill coefficient value of 1.02 and 0.79, respectively, which were not significantly different of unity. α,β-methylene ATP (100µM) was virtually inactive in both species. Pyridoxalphophate-6-azophenyl-2′,4′-disulphonic acid (0.01–30µM) inhibited the ATP-induced currents (I ATP ) with a different potency; being the IC 50 0.6 and 1.8μM in mouse and guinea pig, respectively. In mouse myenteric neurons, I ATP were inhibited by suramin whereas in guinea pig neurons we observed two effects, potentiation and inhibition of these currents. On guinea pig, both effects of suramin had different recovering kinetics and concentration dependency, indicating that they are mediated by at least two different binding sites. Our observations indicate that myenteric P2X receptors in these two species have different pharmacological properties.