Periodic availability: factors affecting alcohol selection in rats.

The joint influence of alcohol availability conditions and alcohol concentration on the acquisition and maintenance of alcohol selection was examined in non-alcohol preferring Sprague-Dawley rats. Relative alcohol selection increased gradually in rats given periodic access to 10% alcohol but was immediately apparent in rats given periodic access to 5% alcohol. Rats given continuous access to alcohol (either forced or choice) did not show similar increases in alcohol selection until switched to the periodic schedule. The increases were not sustained in any group when alcohol became continuously available. Comparable increases in alcohol selection were evident in rats given periodic access to alcohol on various fixed schedules or on a random schedule. Several factors appear to influence the degree of alcohol selection under conditions of periodic availability: alcohol concentration, nature of prior experience with alcohol, the frequency of access to alcohol, the regularity of the periodic access to alcohol, and differences in individual responsivity to the schedule variable.