Identification and characterization of genes that are involved in reward mechanisms in ethanol self-administration

Abstract: Alcohol addiction is one of the most common drug addictions amongst societies. Alcohol abuse, can lead serious injuries, severe diseases or even death. Despite intensive research, complete knowledge about alcohol addiction and a specific "ethanol receptor" has not been found yet. However, persistent researchers discovered that ethanol consumption and abuse is associated to the brain reward pathway and acts on the receptors of the system to elicit addiction. This project aimed to identify and characterize genes involved in the vulnerability for developing alcohol addiction. mRNA expression levels of neurotransmitter receptors were correlated to ethanol self administration in 11 rat brains. Measurement of the neurotransmitter receptor's mRNA expression was carried out by using quantitative real-time PCR. The tested brain areas were the ventral tegmental area (VTA), nucleus accumbens ( NAc), substantial nigra (Sn) and the caudate putamen (CPu). These areas have important roles in the reward pathway and contain the mesocorticolimbic dopamine pathway, which is believed to be behind the reward mechanisms. We found that the iontropic glutamate AMPA receptor subtype 3 (GluR3) in VTA correlated with ethanol self-administration. Two additional correlations were found in the NAc; the glutamate AMPA receptor subtype 3 (GluR3) and the dopamine receptor subtype 2 (DR2). Glutamatergic and dopaminergic receptors in VTA and NAc have been pointed out to be important in alcohol abuse, addiction behavior and reward. The correlated results showed a collaboration between the glutamatergic and the dopaminergic system in the VTA and NAc, which actuate alcohol addiction and behavior.