Effects of P 1 and P2 receptor antagonists on β,γ ‐methyleneATP‐ and CGS21680‐induced cyclic AMP formation in NG108‐15 cells

We have previously shown that ATP increased cyclic AMP in NG108‐15 cells, which was inhibited by P 1 receptor antagonist methylxanthines. In the present study, we examined the effects of P 1 and P2 receptor antagonists on cyclic AMP formation induced by β,γ‐methyleneATP (β,γ‐MeATP) and CGS21680, an A 2A adenosine receptor agonist, in NG108‐15 cells. β,γ‐MeATP and CGS21680 increased intracellular cyclic AMP with EC 50 values of 8.0±0.98 μ M ( n =4) and 42±7.5 n M ( n =4), respectively. Several P 1 receptor antagonists inhibited both β,γ‐MeATP‐ and CGS21680‐induced cyclic AMP increase with a similar rank order of potency; ZM241385>CGS15943>XAC>DPCPX. However, the pK i values of these antagonists for β,γ‐MeATP were larger than those for CGS21680. Alloxazine, a P 1 receptor antagonist, and several P2 receptor antagonists (PPADS, i PPADS, reactive blue‐2) inhibited β,γ‐MeATP‐induced response, while these antagonists little affected CGS21680‐induced one. Suramin was effective only for β,γ‐MeATP‐induced response at 1 m M . 2‐chloroadenosine (2CADO) and 2‐chloroATP (2ClATP) increased cyclic AMP with similar potencies. The effects of these agonists were both inhibited by ZM241385, but only 2ClATP‐induced response was inhibited by PPADS. ATP‐ and β,γ‐MeATP‐induced responses were little affected by α,β‐methyleneADP, a 5′‐nucleotidase inhibitor. These results clearly demonstrate that ATP‐stimulated cyclic AMP formation can be distinguished from the A 2A receptor agonist‐induced one by using the several P 1 and P2 receptor antagonists.British Journal of Pharmacology (2000) 129 , 291–298; doi: 10.1038/sj.bjp.0703053