Figure 2.
The µ-opioid receptor antagonist, GSK1521498, decreased cocaine, heroin and alcohol seeking under second-order schedules of reinforcement and on voluntary alcohol consumption. The highly selective µ-opioid receptor antagonist, GSK1521498, was effective in reducing cocaine (in a), heroin (b) or alcohol (c(i)) seeking in rats responding for these drugs under second-order schedules. GSK1521498 also reduced alcohol intake (c(ii)) during the 20 min drinking period earned by prior alcohol-seeking responses reinforced by the alcohol-associated CS during the prior 15 min fixed interval. Data are mean + s.e.m. seeking responses/fixed interval 15 min; alcohol intake is expressed as grams per kilogram body weight. GSK1521498 was given at three different doses (0.1, 1, 3 mg kg−1) and injected intraperitoneally (IP) 20 min before session. (Online version in colour.)