Psychosocial stress and chronic ethanol ingestion in male rats: effects on elevated plus maze behavior and ultrasonic vocalizations.

Psychosocial stress is known to enhance anxiety levels in rodents. The present study evaluated the effect of long-term ingestion of ethanol (EtOH) on anxiety levels of male Long Evans rats housed either singly or in triads (three/cage). Based on measures of offensive and defensive behaviors, triad-housed rats were designated as being dominant, subdominant or subordinate. The effect of chronic ingestion of a 6% EtOH solution was assessed on behaviors in the elevated plus maze (EPM) test, and on air-puffs elicited 22 kHz ultrasonic vocalizations (USV). EtOH naïve dominant rats showed less anxiogenic-like (open arms time) and displacement behavior (grooming), but more risk assessment behavior (stretch-attend postures) than their cage-mates or the single-housed rats. Intake of EtOH prior to the EPM test was lower in dominant and single-housed rats compared to subdominant and subordinate rats. Triad-housed rats, but not the single-housed rats, decreased their intake of EtOH after the EPM test. Overall, EtOH intake had an anxiolytic effect in all rats, but the effect was most prominent in single-housed rats. Furthermore, EtOH intake decreased air-puff induced USVs of triad-housed rats, but increased USVs of single-housed rats. These data indicate that housing condition and rank status influence the emotional state of male rats. Furthermore, the anxiolytic effect of voluntarily ingested EtOH was depended on these variables.