Effects of morphine, naltrexone, and dextrorphan in untreated and morphine-treated pigeons.

摘要: Six pigeons, trained to peck a response key on fixed-ratio 20 schedule of food reinforcement, were used examine the effects morphine, naltrexone, and dextror- phan, before, during, after chronic treatment with increasing doses morphine (10.0-100.0 mg/kg/day). Tolerance developed rate-decreasing effect daily maintenance within 2 days each dose increase. A small amount tolerance supersensitivity naltrexone was evident 1st week (10.0 Con- tinued administration (32.0-100.0 mg/kg/day) produced further supersensitiv- ity as evidenced by 5-fold increase in 1,000-fold decrease necessary suppress responding. By 4th (100.0 mg/kg/day), modest had also dextrorphan. Suppression responding but not or dextrorphan, accompanied loss body weight over 1- 2-h session morphine-main- tained pigeons; both reduced rates occurred termination treatment. Sensitivity near normal 10 following The dramatic changes sensitivity injections, well ability generate complete dose-effect curves single session, indicate that this behavioral preparation may provide sensitive concurrent measures narcotic supersensi- tivity antagonists pigeon.