Effects of Chronic Ethanol Consumption and Aging on Dopamine, Serotonin, and Metabolites

Abstract

This study examined the hypothesis that chronic ethanol consumption results in significant abnormalities in both the dopaminergic and the serotonergic system of aged rats. Levels of dopamine (DA), serotonin [5-hydroxytryptamine (5-HT)], 3,4-dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindole-3-acetic acid (5-HIAA) were determined in brain areas of both the nigrostriatal and mesocorticolimbic DA systems in 5-, 14-, and 24-month-old male Fischer 344 rats. Aging was associated with a reduced concentration of DA in the striatum (ST), ventral tegmental area (VTA), and ventral pallidum (VP) and an increased concentration of 5-HIAA in the ST, globus pallidus, nucleus accumbens, frontal cortex, and VP. In addition, there was an increase in the 5-HIAA/5-HT ratio in all brain areas analyzed. Six weeks of ethanol consumption was accompanied by significant changes in mesocorticolimbic brain areas. In the VTA of 5-monthold ethanol-fed rats DA content was decreased to the levels found in aged rats, e.g., 24 months of age. Ethanol also significantly lowered 5-HT and 5-HIAA contents in the VTA and reduced DOPAC and 5-HIAA levels in the VP. In addition, ethanol blunted the normal age-related increase in 5-HIAA/5-HT ratio in the VTA, VP, and substantia nigra. It is interesting that although the age-related changes were found in both nigrostriatal and mesocorticolimbic brain areas, the ethanol-associated effects were found only in brain areas of the mesocorticolimbic system. The changes in DA and 5-HT function that accompany aging and ethanol consumption may contribute to the problems in motor function and ethanol abuse found in the aged.

Effects of Lifelong Ethanol Consumption on Brain Monoamine Transmitters in Alcohol-Preferring Alko Alcohol (AA) Rats

“…The results are in line with earlier reports showing reduced concentrations of dopamine in the brain of aged rats, especially in the dopamine rich areas [3,4,5,7]. They are also consistent with investigations reporting age-related decline in dopamine D 1 and D 2 receptors [10,11].…”

“…Several studies have demonstrated selective changes in the concentration of noradrenaline, dopamine and 5-HT in different areas of rat CNS during aging [3,4,5,6,7]. Studies conducted with the mutant zitter rats have demonstrated age-related degenerative changes in the different terminal areas of the ascending dopaminergic and 5-hydroxytryptaminergic neuronal systems [6,8].…”

Prolonged Exposure to Intermittent Alcohol Vapors Blunts Hypothalamic Responsiveness to Immune and Non‐Immune Signals

“…Alcohol is unique as a drug because it seems to vehicle LPS LEE ET AL. have multiple primary targets that include ligand-gated ion channels (such as those associated with GABA, NMDA, 5-HT), transporters, catecholamines, serotonin, glutamate, opioids, dopamine, and acetylcholine (Eckardt et al, 1998;Faingold et al, 1998;Woods and Druse, 1996). As these neurotransmitters exert both stimulatory and inhibitory effects on the PVN, and as their responses to long-term alcohol exposure is not fully understood, it is very difficult to predict which ones are influential in our model.…”

Effects of chronic ethanol treatment on monoamine levels in rat hippocampus and striatum

“…In addition, chronic ethanol consumption has been shown to decrease the content of DA and its metabolites and of 5-HIAA in striatal tissue 24 h after cessation of ethanol intake (23), indicating the occurrence of changes in monoamine turnover. Other investigators (36) observed an increase in the 5-HIAA/5-HT ratio in brain areas, including the striatum, of aged rats.…”