VOLUNTARY ETHANOL-CONSUMPTION IN RATS - THE IMPORTANCE OF THE EXPOSURE PARADIGM IN DETERMINING FINAL INTAKE OUTCOME

The present investigation examined two methods of ethanol presentation to laboratory rats that have been used to examine the mechanisms medi ating voluntary ethanol intake in animals. Experiment 1 examined wheth er a restricted access procedure had any significant and meaningful re lationship in individual animals to drinking behavior in an unrestrict ed 24 h paradigm. An unselected strain of rats was given free access ( unrestricted 24 h free choice) to ethanol and water, and later exposed to a restricted 10 min access to ethanol. A significant positive rela tionship between the absolute amount of ethanol consumed in the 24h ac cess paradigm and the amount ingested by the same animals in the restr icted access procedure was demonstrated. Experiment 2 examined the ext ent to which a forced choice preference testing procedure, commonly us ed in screening ethanol-preferring P rats, was in and of itself suffic ient to produce increased levels of ethanol consumption in unselected Long-Evans rats. Results indicated that subjects receiving only 4 days of forced exposure to 10% ethanol consumed, over the next eight ethan ol presentations, levels of ethanol exceeding 5 g/kg with a 0.60 prefe rence ratio. A microstructural analysis of the pattern of free choice ethanol intake following forced ethanol exposure (Experiment 3) reveal ed that rats consumed ethanol within short discrete bouts with the lar gest of these daily bouts consisting of approximately 4 ml (0.75 g/kg) of 10% ethanol. The amount consumed during the restricted access bout of Experiment 1 was seen to be within the range of the bouts recorded in Experiment 3. These results suggest that consumption of ethanol du ring the restricted access may simulate an individual bout of ethanol intake during non-restricted access. The results support the notion th at many of the different ethanol drinking models used may have a commo n basis and that the assessment of the amount and pattern of intake ac ross methods and strains may represent different but equally valid app roaches to the study of the same underlying mechanisms.