Aversion to acetaldehyde: differences in low-alcohol-drinking (UChA) and high-alcohol-drinking (UChB) rats

We have previously found the existence of a relation between activity of the brain mitochondrial aldehyde dehydrogenase (ALDH2) and consumption of ethanol in rats of the low-alcohol-drinking (UChA) and the high-alcohol-drinking (UChB) strains. The aim of the present study was to determine whether UChA and UChB rats also differed in sensitivity to the aversive effects of acetaldehyde (AcH). Aversion to AcH was studied by using a conditioned taste aversion (CTA) paradigm. Ethanol naive UChA and UChB rats were administered AcH intraperitoneally (50, 100, or 150 mg/kg) or saline and exposed to a banana-flavored solution during five conditioning trials. A strong dose-dependent CTA to AcH was found in UChA rats, whereas UChB rats did not show a CTA to any dose of AcH. At equal doses of AcH, cerebral venous blood AcH levels in UChA rats were consistently higher than in UChB rats, a finding that may reflect the previously observed differences in the activity of ALDH2 between these strains. However, this observation is unlikely to explain fully the differences observed because aversion to AcH was developed in the UChA strain at blood levels of AcH that did not produce any aversion in the UChB strain. These results support the suggestion that, for the first time, differences in central or systemic effects of AcH per se may play a major role in determining the aversion to AcH in drinker and nondrinker animals.