Immunostained serotonergic fibers are decreased in selected brain regions of alcohol-preferring rats.
The levels of serotonin (5-HT) and 5-hydroxyindole-acetic acid (5-HIAA) are decreased in the hippocampus, nucleus accumbens, and cortex of selectively bred alcohol-preferring (P) rats, compared with the alcohol-nonpreferring (NP) rats. In this study, we have confirmed these findings by immunocytochemistry and quantitative image analysis which indicates that there is a reduction of 5-HT immunostained fibers in several brain areas of alcohol-naive P rats. Three major areas possibly related to alcohol drinking, hippocampus, accumbens, and cortex, were examined. Pathways to these areas were also examined. The 5-HT fiber bundles had the same pattern in P and NP rats. However, in the terminal regions of the ventral hippocampus, the amount of 5-HT fibers was reduced in P rats as compared with NP rats. The 5-HT fibers in the hilus and CA4 of the dentate gyrus were also significantly decreased in the P rats. No differences in fiber density were seen in the anterior nucleus accumbens, but a significant decrease was seen in the middle medial and posterior accumbens of P rats. In the cortical regions examined, decreases in 5-HT fibers were observed in the posterior cingulum and anterior frontal cortex, but not in the insular frontal cortex of P rats. These observations indicate that there are quantitative decreases in 5-HT innervations or that the 5-HT in some 5-HT fibers is reduced to a level undetectable by immunocytochemistry in the brains of P rats when compared with that of NP rats.
Zhou
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FC
Department of Anatomy, Indiana University School of Medicine, Indianapolis 46202.
Bledsoe
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Lumeng
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Li
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TK
D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D001921:Brain / Q000378:metabolism / Q000648:ultrastructure*; D002755:Choice Behavior / Q000502:physiology*; D000431:Ethanol; D005260:Female; D007150:Immunohistochemistry / Q000379:methods; D009412:Nerve Fibers / Q000378:metabolism / Q000648:ultrastructure*; D051381:Rats; D012016:Reference Values; D012701:Serotonin / Q000378:metabolism*; D013194:Staining and Labeling; D014018:Tissue Distribution
D012701:Serotonin; D000431:Ethanol