Figure 4.

Effect of different antagonists and Zn²⁺ on ATP-induced outflow of [³H]-NA. Isolated guinea-pig right atrium preparations were superfused and subjected to ATP (1 mM) application, according to the experimental protocol shown in Figure 1b. DPCPX (250 nM), DMPX (250 nM), reactive blue 2 (RB2, 10 μM), Zn²⁺ (50 μM) and PPADS (30 μM) were perfused 10 min before ATP application and thereafter. The net tritium release evoked by ATP was calculated by the area-under-the-curve method and expressed in fractional release (%). Data show the means±s.e.mean of 6–8 identical experiments. ^**P<0.01 indicates significant differences between ATP-evoked tritium outflow in the absence and presence of drugs or Zn²⁺, calculated by ANOVA followed by Dunnett test.