A comparison of the expression of α-synuclein mRNA in the brain of rats with different levels of alcohol consumption

Recent studies suggest that the presynaptic protein α-synuclein has one of the key positions in the regulation of the functions of the dopamine system and the mechanisms of different addictions, including alcohol addiction. However, the role of α-synuclein at certain stages of addiction formation is still unclear. In particular, on the basis of the data from different studies it is not possible to make an unambiguous conclusion on the direct influence of alcohol on the expression of the α-synuclein gene in the brain and, if it occurs, whether these changes are a neuroadaptive response or, in contrast, one of key links of addiction pathogenesis. The task of the current study was to compare the expression of the α-synuclein gene in the brain of animals that chronically consumed alcohol in a “free-choice᾿model and had different level of its consumption. From the 60th to 120th days of life, outbred male Wistar rats were maintained in individual cages with two drinking bottles that contained 10% ethanol solution and water. Ethanol consumption was evaluated daily in g/kg body weight and the preference was estimated as the percentage of the total volume of liquid consumed. At an age of 120 days, the animals were decapitated and the midbrain, striatum, hypothalamus, and amygdala were dissected. The levels of expression of α-synuclein mRNA were determined by the real-time quantitative polymerase chain reaction (RT-PCR). Our results indicate that animals with a high level of alcohol consumption (a daily average consumption of ethanol 10.4 ± 0.79 g/kg) had significantly decreased indices of α-synuclein expression in the midbrain (by 45%) and hypothalamus (by 42%) as compared to animals with a permanently low level of consumption (3.6 ± 0.46 g/kg). These changes were found in the brain areas that form the dopaminergic pathways in the brain but not in the areas that are the targets of dopamine neurons. The data we obtained support the hypothesis on the possible “protective᾿role of α-synuclein in the dopamine-synthesizing brain structures of animals with a low level of alcohol preference and the ability to “control᾿intake by its maintenance at a constant level.