The impact of moderate daily alcohol consumption on aggression and the formation of dominance hierarchies in rats.
OBJECTIVE
Group-housed male rats form social hierarchies, and under these conditions, it has been reported that subordinate (SUB) rats consume more alcohol than dominant (DOM) rats. We tested the hypothesis that a history of drinking alcohol would cause SUB rats to consume even greater amounts of alcohol.


METHODS
Male Long-Evans rats were trained to drink 10% alcohol or a sucrose/quinine solution equal in calories for 1 h/day using a sucrose-fading procedure. Subsequently, rats were housed in colonies (four males, two females) in a visible burrow system (VBS) for 14 days. Individual control male rats were housed in a tub cage with one female. Rats were removed from the VBS (or control environment) daily and given 1 h to drink alcohol or sucrose/quinine.


RESULTS
Colonies given daily access to sucrose/quinine formed clear DOM/SUB relationships in all measured parameters. Alcohol-drinking colonies failed to establish a dominance hierarchy and displayed little aggression, with an average of 14.6 +/- 6.1 offensive attacks compared with 58.5 +/- 12.3 attacks carried out by DOM sucrose/quinine rats. During VBS housing, alcohol and sucrose/quinine intake decreased independent of housing environment or social status.


CONCLUSIONS
Contrary to prior reports of the effect of alcohol on aggressive behavior, moderate daily alcohol intake before and during VBS housing reduced aggression and precluded the formation of a dominance hierarchy in rats.
Duncan
Elizabeth A
EA
Program in Neuroscience, University of Cincinnati, Cincinnati, OH, USA. duncanel@mail.nih.gov
Tamashiro
Kellie L K
KL
Nguyen
Mary M N
MM
Gardner
Stacy R
SR
Woods
Stephen C
SC
Sakai
Randall R
RR
D000374:Aggression / Q000187:drug effects*; D000428:Alcohol Drinking / Q000523:psychology*; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D002492:Central Nervous System Depressants / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D003345:Corticosterone / Q000097:blood; D003624:Darkness; D004327:Drinking Behavior / Q000187:drug effects; D000431:Ethanol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D008027:Light; D008297:Male; D011803:Quinine / Q000008:administration & dosage; D051381:Rats; D020318:Rats, Long-Evans; D012054:Reinforcement, Psychology; D012646:Self Administration; D012930:Social Dominance; D013395:Sucrose / Q000008:administration & dosage; D013739:Testosterone / Q000097:blood; D013997:Time Factors
D002492:Central Nervous System Depressants; D000431:Ethanol; D013739:Testosterone; D013395:Sucrose; D011803:Quinine; D003345:Corticosterone