Figure 2. Effect of W-15 and W-18 on opioid receptor–mediated G_αi signaling.

The G_i-mediated inhibition of cAMP production was determined as previously described (9–11). Both W-15 and W-18 showed no agonist activity at DOR (A), KOR (B), MOR (C), and nociceptin (NOP) (D) receptors and no antagonist activity at DOR (E), KOR (F), or MOR (G) receptors. Normalized results represent mean ± SEM of 3 independent experiments, each performed in triplicate (0% activity for vehicle activity; 100% for reference activity), and were analyzed in Prism.