Association between Low Contents of Dopamine and Serotonin in the Nucleus Accumbens and High Alcohol Preference

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Abstract
The contents of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin (5-HT), and 5-hydroxy-indoleacetic acid (5-HIAA) were determined in the nucleus accumbens (ACB), frontal cortex (FR), anterior striatum (AST), and hippocampus (HIP) of adult male rats from the F2 generation of P×NP intercrosses. Rats were tested for their alcohol preference and were divided into two groups, depending on their alcohol intake. Rats in the high drinking group (n= 11) had ethanol intakes >5 g/kg/day, whereas the low drinking group (n= 15) had values < 1 g/kg/day. The content of DA in the ACB was lower (p < 0.001) in the high alcohol drinking group (46 ± 2 pmol/mg tissue) than in the low intake rats (61 ± 3 pmol/mg tissue). However, the contents of DOPAC and HVA in the ACB were similar for both groups. There were no differences between the two groups in the contents of DA in the FR or AST. The content of 5-HT in the ACB was lower (p < 0.05) in high alcohol drinking rats (6.3 ± 0.3 pmol/mg tissue) than in the low intake group (7.0 ± 0.2 pmol/mg tissue). The content of 5-HIAA in the ACB of the high intake rats was also lower than the level for the low drinking rats. There were no differences in the contents of 5-HT or 5-HIAA in the FR, HIP, and AST between the two groups. The results confirm a phenotypic association between abnormal DA and 5-HT systems projecting to the ACB and high alcohol drinking behavior in the P line of rats.