(4) alcohol dependent (n = 4), trained to self-administer alcohol vs. water for 3 weeks (30 minute access to alcohol, 5 days a week) and exposed to intermittent chronic alcohol vapors for the following 6 weeks to induce dependence during which they were tested for alcohol intake via alcohol self-administration twice a week; (5) prolonged nondependent (n = 6), trained to self-administer alcohol vs. water for 3 weeks and housed under control air conditions (no alcohol vapors) for the following 10 weeks during which they were tested for alcohol self-administration twice a week up to 6 weeks and were discontinued from testing for the additional 4 weeks; (6) prolonged dependent (n = 4), trained to self-administer alcohol vs. water for 3 weeks and exposed to intermittent chronic alcohol vapors for the following 10 weeks during which they were tested for alcohol self-administration twice a week up to 6 weeks and were discontinued from testing for the additional 4 weeks. The main difference between the nondependent and dependent conditions is the exposure to intermittent alcohol vapors in the dependent groups and higher intake of alcohol during self-administration sessions. After several weeks of intermittent vapor exposure, dependent animals show mild physical dependence
