Fig. 5.

Effects of intra-ventral tegmental area (VTA) microinjections of SKF 82958 on place conditioning in morphine-dependent (black bars) and nondependent (gray bars) rats. Rats with unilateral cannulae in the VTA or just dorsal to the VTA were implanted with placebo or morphine pellets and, 3 days, later underwent place conditioning with systemic naloxone (0.01 mg/kg, SC), intracranial SKF 82958 (2 μg, intra-VTA or dorsal control), or a combination of intracranial SKF 82958 and systemic naloxone. Data from microinjections of SKF 82958 into dorsal control regions are shown to the right of the dashed line. 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, 7–20 rats per group