Chart 1. Agonist and Antagonist Ligand Probes of the P2Y₁₄Ra.

^a Endogenous agonists 1 and 2 have functional EC₅₀ values at the hP2Y₁₄R of 160 and 261 nM, respectively.⁴⁵ Antagonist 3 is highly potent at the hP2Y₁₄R (K_B from Schild analysis = 0.434 nM)¹⁴ but suffers from adverse physicochemical properties (highly hydrophobic/amphipathic) that make dissolution and purification difficult. Fluorescent antagonist 4 is highly potent at the hP2Y₁₄R (functional K_i = 0.080 nM).¹⁵.