Fig. 1.

The effects of the D1 receptor agonists SKF 82958 and SKF 81297 on place conditioning in morphine-dependent (black bars) and nondependent (gray bars) rats. Rats were implanted with placebo or morphine pellets and, 3 days later, underwent place conditioning with either a naloxone (0.01 mg/kg, SC), SKF 82958 (1.0 mg/kg, SC), or a mixture of naloxone and SKF 82958; or b naloxone (0.01 mg/kg, SC), SKF 81297 (1.0 mg/kg, SC), or a mixture of naloxone and SKF 81297. Data are expressed as the change in time spent in the drug-paired side after conditioning minus the time spent in the drug-paired side before conditioning (means+SEM). Significant changes in time spent in the drug-paired chamber after conditioning compared to before conditioning are: *p<0.05, **p<0.01, Fisher’s protected t tests, 8–13 rats per group. Nal naloxone, SKF SKF 82958 or SKF 81297 (see panel heading)