Levels of secreted BDNF were measured using in situ ELISA. Data is normalized to the maximal response produced by stimulation of endogenous EP2 receptors. A, The S1R reference agonists 4-PPBP and (+)-SKF10047, exert a robust BDNF secretion response that is reduced by a S1R-selective dose of the S1R reference antagonist BD1063. However, BD1063 does not modify the PGE2 stimulated response mediated by EP2R. B, At a concentration that causes maximal secretion of BDNF via interactions with the EP2R, PGE2 (10 μM) is unable to displace specific bound radioligand from either S1R or S2R. [3H]-(+)-pentazocine was the radioligand used to probe the S1R in MCF-7 cells stably expressing the cloned human S1R, while [3H]-DTG was used as the radioligand to probe the S2R in untransfected MCF-7 cells.