Limited-access consumption of ascending ethanol concentrations in alcohol-preferring, nonpreferring, and Sprague-Dawley rats.

BACKGROUND: Ethanol intake and preference differences between the selectively bred alcohol-preferring (P) and nonpreferring (NP) rats have generally been studied in a continuous-access paradigm using 10% ethanol. Little is known about the consumption of lower concentrations of ethanol in these lines or consumption of a wide range of ethanol concentrations in limited-access paradigms. Recently, limited-access paradigms have been used to study the biological and pharmacological mechanisms of ethanol consumption in animal models. Such research would be informed by studies investigating ethanol oral self-administration within a limited-access context. Therefore, the current study addressed P, NP, and Sprague-Dawley (SD) rats' consumption of a wide range of ethanol concentrations in a 2-bottle-choice, limited-access procedure. METHODS: Male P, NP, and SD rats were given concurrent access to water and ethanol solutions for 1 h/d, 7 d/wk. Ethanol solutions were presented in an ascending series ranging from 0.01 to 20% (v/v) over 55 days. Ethanol intakes (g/kg), volumes of solutions consumed (mL/kg), and preference ratios were assessed for each rat line at each concentration. RESULTS: Clear differences among the 3 types of rats emerged at an ethanol concentration of 4%, although differences between P and NP rats emerged at concentrations as low as 1.8%. Alcohol-preferring rats almost exclusively preferred ethanol solutions over water at ethanol concentrations of 4% and above, whereas SD and NP rats' preference ratios were more variable. CONCLUSIONS: The results suggest that differences between P and NP rats exist at ethanol concentrations lower than those previously studied in continuous-access paradigms. They also provide a current description of the ranges of ethanol concentrations preferred by P, NP, and SD rats.