Time-dependent alterations in ethanol intake in male wistar rats exposed to short and prolonged daily maternal separation in a 4-bottle free-choice paradigm

Background: Previous studies have shown that maternal separation can be used in animal studies of early environmental influence on adult ethanol intake. These studies have shown that short daily separations result in low ethanol intake, whereas prolonged separations relate to an enhanced risk for a high ethanol intake. The aim of the present study was to further examine the long-term effects of early-life events on ethanol intake. Methods: Rat pups were exposed to 15 minutes (MS15) or 360 minutes (MS360) of daily maternal separation during postnatal days 1 to 21 or kept under normal animal facility rearing (AFR) conditions. In adulthood, male rats were given free access to 5, 10, and 20% ethanol, in addition to water, in a 4-bottle-choice paradigm. Results: No differences in total ethanol intake or preference between the 3 experimental groups were found. The 54-day drinking period was divided into acquisition, stabilization, and maintenance phases for analysis of time and group differences. The MS15 rats increased ethanol intake over time; they mostly consumed 5% ethanol and had a low intake of 20% ethanol throughout the experiment. MS360 rats increased ethanol intake, changed preference from 5% to 20% ethanol, and had a higher increase in intake of 20% ethanol over time. The ethanol intake and preference in the AFR rats were more similar to that of the MS360 rats. Conclusions: Time-dependent changes were observed in the preferred choice of low versus high ethanol concentrations in MS15 and MS360 rats. The results support previous findings suggesting that MS15 can be used as a model for environmental protective factors and that MS360 represents a risk environment for acquisition of a high adult ethanol intake.