Figure 3: U50,488 reinstates ethanol-seeking behavior. Rats () were trained to self-administer a 10% ethanol solution using standard operant procedures, and then lever pressing for ethanol was subsequently extinguished. Responding on an inactive lever was measured as an indication of general motor activity. Following extinction, rats received priming injections of U50,488 (0–10 mg/kg, i.p.) and were tested for reinstatement of responding on the previously ethanol-associated lever. Tests were conducted every 3-4 days, with rats experiencing extinction sessions daily between test days. Data are expressed as the mean number of lever responses ± SEM during ethanol self-administration sessions. compared to self-administration, extinction, and 10.0 mg/kg U-50,488 groups, Tukey’s test.