Social interaction opportunity and intermittent presentations of ethanol sipper tube induce ethanol drinking in rats

We evaluated the effects of social interaction opportunity (SIO) and intermittent presentations of the ethanol sipper tube (IS) on autoshaping of ethanol drinking in nondeprived rats. Rats were assigned to one of seven groups. Two groups experienced brief IS, either paired with or randomly related to the response-independent raising of a guillotine door (D) revealing the presence of a conspecific male rat in a holding cage (SIO). Two control groups received similar training, respectively, except that the D revealed an empty cage, whereas a third control group received IS but neither D nor SIO. For two additional control groups, the ethanol sipper tube was continuously available during the session, with and without SIO, with both groups receiving intermittent D. In IS conditions, procedures with SIO induced more ethanol intake than did non-SIO procedures, indicating that SIO contributed to ethanol intake, but D procedures did not differ from non-D procedures, indicating that ethanol drinking was not related to the operation of the door. Groups that received training procedures providing for both SIO and IS showed more rapid initiation of ethanol intake and more rapid escalation of ethanol intake as the concentration of ethanol in the sipper tube conditioned stimulus was increased across sessions. Theoretical accounts, which are based on cue at response manipulandum/autoshaping, schedule-induced polydipsia, incentive sensitization, and intermittency-induced arousal, are considered.