Figure 4.

Incubation of slices with etorphine, oxymorphone, methadone, or oxycodone did not block ME-induced desensitization. A, Sample experiment from a slice that was incubated with etorphine (2 nm, 1 h) before recording the outward current induced by ME (30 μm, 10 min). The ME current peaked (ME1) and declined (ME2) during the 10 min application period. Superfusion with naloxone (Nal; 1 μm) caused an inward current, indicating the presence of etorphine in the slice. B, The same experiment done with slices that were incubated with methadone (1 μm) C, The same experiment done with oxymorphone (1 μm) for 1 h. D, Summarized results plotting the ratio of ME2/ME1 in experiments using slices incubated in buprenorphine (BUP; 5 nm), etorphine (ET; 2 nm), oxymorphone (OM; 1 μm), oxycodone (OC; 1 μm), or methadone (MD; 1 μm) for 1 h before the experiment. There was a marked decrease in the ME current in all experiments except in slices incubated in buprenorphine. Yoh, Yohimbine.