Juan Ramirez-Martinez - Two suramin binding sites are present in guinea pig but only one in murine native P2X myenteric receptors

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    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 60 mV. Concentrationresponse curves for ATP (13000 μM) yielded EC50 values of 114 and 115 μM 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 (100 μM) was virtually inactive

    in both species. Pyridoxalphophate-6-azophenyl-2,4-disulphonic   acid (0.0130 μM)   inhibited the ATPinduced currents (IATP) with a   different potency; being the IC50 0.6 and   1.8 μM in mouse   and guinea pig,

    respectively. In mouse myenteric neurons, IATP 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.

      Address (URL): http://www.sciencedirect.com/science/article/pii/S0014299909008474