Chronic morphine withdrawal-induced hyperalgesia and allodynia in sham-operated and L5 nerve-transected rats
| n | Sham-operated rats | L5 nerve-transected rats | ||||
|---|---|---|---|---|---|---|
| Saline | Morphine | Saline | Morphine | |||
| Thermal hyperalgesia (tail-flick latency in seconds) | 8 | 5.3 ± 0.2 | 3.7 ± 0.2* | 3.2 ± 0.2 | 2.8 ± 0.3 | |
| Mechanical hyperalgesia (paw-pressure threshold in grams) | 8 | 98.5 ± 4.2 | 69.4 ± 2.4* | 48.2 ± 3.0 | 35.3 ± 1.8*,2-160 | |
| 2 gm | 0 | 3.9 ± 0.5* | 7.9 ± 0.6 | 14.3 ± 2.1*,2-160 | ||
| Mechanical allodynia (number of paw withdrawals per 30 stimuli) | 8 | 12 gm | 0.1 ± 0.2 | 6.9 ± 0.7* | 15.4 ± 0.9 | 20.1 ± 0.8*,2-160 |
Pretreatments consisted of two daily injections of morphine (10 mg/kg, s.c.) or saline administered on postoperative days 6–10. Withdrawal-induced hyperalgesia and allodynia were recorded 16 hr after the last injection of morphine or saline (i.e., on day 11). Data are expressed as mean ± SEM.
↵* p < 0.05 versus respective saline-treated rats;
↵F2-160 p < 0.05 compared with chronic morphine-treated, sham-operated rats (Bonferroni test).