Maternal separation alters acquisition of ethanol intake in male ethanol-preferring AA rats

Prolonged daily maternal separation can increase the risk for developing substance abuse, whereas brief maternal separation has been reported to induce positive behavioral effects, decrease voluntary ethanol intake and induce long-lasting changes in brain opioid peptides. The ethanol-preferring AA (Alko, Alcohol) rats have altered basal levels of endogenous opioid peptides that may relate to their high voluntary ethanol intake. The purpose of this study was to investigate whether maternal separation could affect acquisition of ethanol intake in AA rats.

The rat pups were exposed to 15 min (MS15) or 360 min (MS360) of maternal separation during postnatal day 1-21, while control rats were exposed to normal animal facility rearing. As adults, the male rats were gradually introduced to increasing concentrations of ethanol. Furthermore, the effect of restraint stress on voluntary ethanol intake was investigated.

The MS15 rats reached a high voluntary ethanol intake later than MS360 and control rats. The MS15 rats had a lower ethanol intake and preference at 8% ethanol compared to MS360 rats and lower ethanol intake compared to control rats. MS15 rats also had a lower 10% ethanol intake in comparison with MS360 rats. Restraint stress decreased the ethanol intake in MS15 and MS360 rats, whereas the ethanol intake in control rats was unaffected.

We have previously shown that prolonged periods of maternal separation in Wistar rats result in an increased ethanol intake later in life. This was not repeated in this study, using AA rats with an inherent high ethanol intake. However, it is shown that brief maternal separation can delay acquisition of high ethanol intake and in addition decrease voluntary ethanol intake and preference in AA rats. Maternal separation for 15 min is therefore suggested to protect against high voluntary ethanol intake later in life.