Relationship between ethanol's acute locomotor effects and ethanol self-administration in male Long-Evans rats. 2008

Ann M Chappell, and Jeff L Weiner
Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 57157, USA.

BACKGROUND Human studies have suggested an important relationship between ethanol sensitivity and risk of alcoholism. These studies have led some to hypothesize that a low initial sensitivity to ethanol's depressant effects and/or an elevated response to ethanol's stimulant effects may represent important risk factors associated with the development of abusive drinking behavior. Unfortunately, elucidating neurobiologic mechanisms that may underlie these relationships between ethanol sensitivity and ethanol drinking have been hampered by difficulties in modeling some of these interactions in animals. In this study, we re-examined some of these relationships in an outbred strain of rats using continuous access two-bottle choice drinking and a limited-access operant procedure that engenders pharmacologically relevant levels of ethanol intake and permits the discrete assessment of appetitive and consummatory measures of ethanol drinking behavior. METHODS Twenty-three male Long-Evans rats were habituated to a locomotor activity box and then tested for their response to a stimulant (0.5 g/kg) and depressant (1.5 g/kg) ethanol dose. Rats were then trained to complete a lever pressing requirement to gain access to 10% ethanol for 20-minute sessions conducted 5 d/wk for 5 weeks. Appetitive behavior was assessed after 2.5 and 4.5 weeks using 20-minute extinction trials in which ethanol was not presented and lever responses were recorded. Home-cage ethanol preference was also assessed prior to and immediately following the 5-week self-administration regimen using a continuous access, two-bottle choice procedure. RESULTS A significant increase in home-cage ethanol preference was observed following the self-administration procedure, however, neither measure of ethanol preference correlated with average daily ethanol intake during the operant self-administration sessions or with initial sensitivity to ethanol's stimulant or depressant effects. Notably, a significant negative correlation was observed between sensitivity to ethanol's locomotor depressant effect and daily intake during the operant self-administration sessions. No significant relationships were noted between sensitivity to ethanol's locomotor effects and extinction responding. CONCLUSIONS The results of these studies suggest that the well-established relationship between a low level of response to ethanol and increased ethanol consumption reported in human studies can be observed in an outbred rodent strain using a limited-access operant self-administration procedure, but not with home-cage ethanol drinking.

UI MeSH Term Description Entries
D008297 Male Males
D009043 Motor Activity Body movements of a human or an animal as a behavioral phenomenon. Activities, Motor,Activity, Motor,Motor Activities
D003216 Conditioning, Operant Learning situations in which the sequence responses of the subject are instrumental in producing reinforcement. When the correct response occurs, which involves the selection from among a repertoire of responses, the subject is immediately reinforced. Instrumental Learning,Learning, Instrumental,Operant Conditioning,Conditionings, Operant,Instrumental Learnings,Learnings, Instrumental,Operant Conditionings
D000428 Alcohol Drinking Behaviors associated with the ingesting of ALCOHOLIC BEVERAGES, including social drinking. Alcohol Consumption,Alcohol Intake,Drinking, Alcohol,Alcohol Drinking Habits,Alcohol Drinking Habit,Alcohol Intakes,Consumption, Alcohol,Drinking Habit, Alcohol,Habit, Alcohol Drinking,Habits, Alcohol Drinking,Intake, Alcohol
D000431 Ethanol A clear, colorless liquid rapidly absorbed from the gastrointestinal tract and distributed throughout the body. It has bactericidal activity and is used often as a topical disinfectant. It is widely used as a solvent and preservative in pharmaceutical preparations as well as serving as the primary ingredient in ALCOHOLIC BEVERAGES. Alcohol, Ethyl,Absolute Alcohol,Grain Alcohol,Alcohol, Absolute,Alcohol, Grain,Ethyl Alcohol
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012646 Self Administration Administration of a drug or chemical by the individual under the direction of a physician. It includes administration clinically or experimentally, by human or animal. Administration, Self,Administrations, Self,Self Administrations
D051381 Rats The common name for the genus Rattus. Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus
D020318 Rats, Long-Evans An outbred strain of rats developed in 1915 by crossing several Wistar Institute white females with a wild gray male. Inbred strains have been derived from this original outbred strain, including Long-Evans cinnamon rats (RATS, INBRED LEC) and Otsuka-Long-Evans-Tokushima Fatty rats (RATS, INBRED OLETF), which are models for Wilson's disease and non-insulin dependent diabetes mellitus, respectively. Long-Evans Rat,Long Evans Rats,Evans Rats, Long,Long Evans Rat,Long-Evans Rats,Rat, Long-Evans,Rats, Long Evans

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