FIGURE 3.

EP2 and EP4 mediate the negative feedback regulation by PGE₂. A and B, spinal cord cells were stimulated with 1 μg/ml LPS, 3 μm rofecoxib, and the respective EP receptor agonist for 21 h. Protein levels were determined by Western blotting. B, densitometric analysis of at least 2 independent experiments. Student's t test: *, p ≤ 0.05. C, prostanoid concentrations in supernatants of spinal cord cultures that have been stimulated with 1 μg/ml LPS and the respective ONO-AE1–259-01 (EP2 agonist) concentrations. Inset, prostanoid concentrations in cultures treated with the indicated ONO-AE1-329 (EP4 agonist) concentrations. Data are shown as the average of at least 3 independent experiments. Student's t test: *, p ≤ 0.05; **, p ≤ 0.01; ***, p ≤ 0.005.