Monoamine and metabolite levels in CNS regions of the P line of alcohol-preferring rats after acute and chronic ethanol treatment

Abstract

Levels of norepinephrine (NE), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were determined in 8 brain regions of the P line of alcohol-preferring rats following: (a) an IP injection of 2.5 g ethanol/kg body wt; (b) 8 and 15 weeks of chronic free-choice drinking of 10% ethanol; (c) 15 weeks of chronic free-choice drinking of 10% ethanol and 24 hours of withdrawal; and (d) 7 weeks of forced administration of 5% ethanol in liquid diet. One hour after IP injection of 2.5 g ethanol/kg body wt, the levels of DOPAC and HVA increased 20–45% in the cerebral cortex (CTX) and striatum (STR). A 20% lower content of NE in the CTX of the ethanol group was the only other statistically significant difference observed. Chronic free-choice drinking of 10% ethanol for 8 weeks (6.5±0.4 g ethanol/kg/day) or 15 weeks (7.8±0.2 g ethanol/kg/day) and the chronic forced administration of ethanol in liquid diets (up to 13.2±0.2g ethanol/kg/day) did not produce any consistent pattern of alterations in the levels of the monoamines or their metabolites in the 8 CNS regions. After 15 weeks of chronic free-choice drinking of 10% ethanol, withdrawal from alcohol also did not produce alterations in the content of the monoamines or their metabolites. These data indicate that acute administration of hypnotic doses of ethanol increases the metabolism of specific dopaminergic neurons in the CNS of the P rat, but monoamine levels and metabolism are not altered after chronic (7–15 weeks) alcohol consumption.