Mean (±S.E.) ED50 values for naive, morphine-tolerant, and oxycodone-tolerant adult male DA rats administered i.v. or i.c.v. bolus doses of oxycodone or morphine
| Tolerance Status | ED50 (±S.E.) of Opioid Drug Administered | |||
|---|---|---|---|---|
| i.v. Oxycodone | i.c.v. Oxycodone | i.v. Morphine | i.c.v. Morphine | |
| nmol | ||||
| Naive | 285.3 ± 39.4 | 74.9 ± 6.9 | 1191 ± 159 | 37.3 ± 3.4 |
| Morphine-tolerant | 1110 ± 1243-a | 84.8 ± 8.6 | 4966 ± 1383-a | 98.7 ± 21.43-a |
| Oxycodone-tolerant | 3763 ± 3423-a | 194.1 ± 29.43-a | 3883 ± 2373-a | 70.4 ± 14.83-a |
↵3-a ED50 significantly different (P < .05) from ED50 in naive rats.