Abstract
To clarify the function of P2 receptor subtypes in mouse stomach, the motor responses to ATP, α,β-methyleneATP (α,β-MeATP), P2X receptor agonist, 2-methylthioATP (2-MeSATP), P2Y receptor agonist, and the effects of the desensitisation of P2X receptors with α,β-MeATP and of P2Y receptors with ADPβS were analysed recording the endoluminal pressure from whole-organ. ATP-induced relaxation was antagonised by suramin, non-selective P2 receptor antagonist, by desensitisation of P2Y receptors with ADPβS, and increased by desensitisation of P2X receptors with α,β-MeATP. α,β-MeATP produced biphasic responses: relaxation, reduced by P2X- or P2Y desensitisation, and contraction, almost abolished by P2X desensitisation and potentiated by P2Y desensitisation. 2-MeSATP induced relaxation, which was antagonised by P2Y desensitisation and increased by P2X desensitisation. Tetrodotoxin increased the relaxation induced by purines and deeply antagonised the contraction to α,β-MeATP. Our results suggest that in mouse stomach are present muscular P2Y receptors, subserving relaxation, and neuronal presynaptic P2X receptors, mediating contraction.
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