Abstract
P2X receptor activation by α,β-meATP evoked inward currents in acutely dissociated rat mesenteric artery smooth muscle cells and contractions of whole artery rings.
The selective P2X1 and P2X3 receptor antagonist TNP-ATP inhibited P2X receptor mediated inward currents in response to 3 μM α,β-meATP (an ∼EC90 concentration) with an IC50 of ∼2 nM. This provides further evidence that the P2X receptor underlying membrane depolarisation associated with P2X receptor activation can be accounted for by the expression of P2X1 receptors.
TNP-ATP inhibited α,β-meATP induced contractions with an IC50 of ∼30 μM and had non-specific effects on smooth muscle contraction.
The reduced potency of TNP-ATP in whole tissue experiments probably reflects the breakdown of TNP-ATP by nucleotidases. Thus, TNP-ATP is of limited use in whole tissue experiments as a P2X receptor antagonist.
Keywords: P2X receptors, ATP, artery, contractions, electrophysiology, antagonist
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