Adh1 and Adh1/ 4 knockout mice as possible rodent models for presymptomatic Parkinson's disease

► Adh1−/− and Adh1/ 4−/− mice have higher spontaneous activity compared to WT mice. ► Apomorphine increase locomotor activity in Adh1−/− and Adh1/ 4−/− mice. ► d-Amphetamine increase locomotor activity in Adh1−/− and Adh1/ 4−/− mice. ► Adh1−/− and Adh1/ 4−/− have decreased monoamine levels in several brain regions. Alcohol dehydrogenases (ADH) catalyze the reversible metabolism of many types of alcohols and aldehydes to prevent the possible toxic accumulation of these compounds. ADHs are of interest in Parkinson's disease (PD) since these compounds can be harmful to dopamine (DA) neurons. Genetic variants in ADH1C and ADH4 have been found to associate with PD and lack of Adh4 gene activity in a mouse model has recently been reported to induce changes in the DA system. Adh1 knockout ( Adh1−/−) and Adh1/ 4 double knockout ( Adh1/ 4−/−) mice were investigated for possible changes in DA system related activity, biochemical parameters and olfactory function compared to wild-type (WT) mice. Locomotor activity was tested at ∼7 (adult) and >15 months of age to mimic the late onset of PD. Adh1−/− and Adh1/ 4−/− mice displayed a significantly higher spontaneous locomotor activity than WT littermates. Both apomorphine and d-amphetamine increased total distance activity in Adh1−/− mice at both age intervals and in Adh1/ 4−/− mice at 7 months of age compared to WT mice. No significant changes were found regarding olfactory function, however biochemical data showed decreased 3,4-dihydroxyphenylacetic acid (DOPAC)/DA ratios in the olfactory bulb and decreased homovanillic acid (HVA)/DA ratios in the olfactory bulb, frontal cortex and striatum of Adh1/ 4−/− mice compared to WT mice. Our results suggest that lack of Adh1 alone or Adh1 and Adh4 together lead to changes in DA system related behavior, and that these knockout mice might be possible rodent models to study presymptomatic PD.