Genetics and epigenetics: paternal adolescent ethanol consumption in serotonin transporter knock-out rats and offspring sensitivity to ethanol

RATIONALE: Alcohol use disorder (AUD) is shown to have an overall heritability of around 50%. One of the genes associated with AUD is SLC6A4 (solute carrier family 6 member A4) which codes for the serotonin transporter (SERT). The study looked at serotonin dysfunction on ethanol consumption in adolescents and the subsequent intergenerational effects of drinking by using a rat model: SERT(+/+) (regular functioning), SERT(+/−) (50% transporter reduction) and SERT(−/−) (complete reduction). OBJECTIVES: We investigated sex and genotype differences in ethanol consumption in SERT knock-out Wistar rats (F0) followed by studying behaviour in the offspring (F1) of the male drinkers to assess effects of paternal alcohol consumption. METHODS: An intermittent access two-bottle choice paradigm (IA2BC) was used to yield ethanol drinking behaviour in F0 adolescent Wistar rats. The highest drinking males were mated to alcohol-naive females and their offspring were compared with controls. Drinking behaviour (IA2BC) and ethanol-induced motor coordination effects (via rotarod) were measured in the F1s. RESULTS: F0 drinking saw no SERT genotype differences in males. However, females consumed higher volumes of ethanol compared to males, with SERT(−/−) females showing the highest intake. A clearer genotype effect was seen in the F1 animals, with reduction in SERT activity leading to enhanced ethanol intake in both sexes. Importantly, paternal exposure to ethanol significantly reduced the ethanol induced motor side effects in offspring, independent of sex and genotype. CONCLUSIONS: These indicate a difference in the way genetic factors may act across sexes and suggest the involvement of epigenetic mechanisms in the intergenerational effects of alcohol.