Figure 3. Characterization of EP₁ receptor–promoted desensitization of β₂ AR-mediated ASM relaxation.

(A) No effect of 17-PTP pretreatment was observed on forskolin-mediated ASM relaxation, indicating that the site of EP₁ modulation is likely proximal to adenylyl cyclase (n = 4). (B) Inhibition of phospholipase C (PLC) with U73122 failed to alter the 17-PTP–evoked desensitization of isoproterenol-mediated ASM relaxation. *P < 0.05 versus vehicle-treated rings (n = 4). (C) Ablation of receptor-G_αi coupling with pertussis toxin (PTX) had no effect on the 17-PTP–evoked desensitization of isoproterenol-mediated ASM relaxation. ^‡P < 0.01 versus rings not treated with 17-PTP (n = 4).