Figure 4.

A, superfusate application of 10 μm, 100 μm and 1 mm ATP evoked transient and sustained vasoconstriction. Dashed line represents onset of ATP application. B, filled squares: summary data for six retinal preparations from four animals showing the arteriole response to increasing concentrations of ATP (measured at the end of agonist application, 100 s; *P < 0.05, ^***P < 0.001, relative to baseline). Open circles: pretreatment with the gliotoxin fluorocitrate (150 μm, 45 min) did not affect the ATP-evoked constrictions of retinal arterioles (n = 6 retinal preparations from three animals, not significant for comparison between ATP alone and after pretreatment with fluorocitrate).