TABLE 3.
Summary of hot plate antinociceptive responses in mice lacking β-arrestin1 or β-arrestin2 in response to different opioid agonists
| Morphine | Methadone | Fentanyl | Etorphine | Oxycodone | Heroin | |
|---|---|---|---|---|---|---|
| Hot plate antinociception | ||||||
| βarr1-KO | =a | N.D. | N.D. | N.D. | N.D. | N.D. |
| βarr2-KO | ↑a,,–d | =a,d | =a,d | =a | =d | ↑a |
| Hot plate antinociceptive tolerance | ||||||
| βarr2-KO | ↓b,d | =d | =d | N.D. | =d | N.D. |
=, equivalent to wild type (WT) response at 10 mg/kg s.c.; ↑, significant increase in response; ↓, significant decrease in response; N.D., not determined.