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Eur J Neurosci. 2008 May;27(9):2466-72. doi: 10.1111/j.1460-9568.2008.06201.x.

Augmented brain 5-HT crosses the blood-brain barrier through the 5-HT transporter in rat.

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  • 1Department of Physiology, Toho University School of Medicine, 5-21-16, Omori-nishi, Ota-ku, Tokyo 143-8540, Japan.


The present study re-evaluated an existing notion that serotonin (5-hydroxytryptamine; 5-HT) could not cross the brain to the circulating blood via the blood-brain barrier (BBB). To elevate brain 5-HT alone, 5-hydroxytryptophan (5-HTP; 30-75 mg/kg) was administrated intravenously to anaesthetized rats that had undergone gastrointestinal and kidney resections along with liver inactivation (organs contributing to increasing blood 5-HT after 5-HTP administration). A microdialysis method and HPLC system were used to determine the brain 5-HT levels in samples collected from the frontal cortex. Blood 5-HT levels were determined from whole blood, not platelet-poor plasma, collected from the central vein. We found that blood 5-HT levels showed a significant augmentation whenever brain 5-HT levels were significantly elevated after the administration of 5-HTP in those rats with the abdominal surgical procedures. This elevation was abolished after pretreatment with a selective serotonin reuptake inhibitor (fluoxetine; 10 mg/kg i.v.), although brain 5-HT levels remained augmented. These results indicate that augmented brain 5-HT can cross the BBB through the 5-HT transporter from the brain to the circulating blood.

[PubMed - indexed for MEDLINE]
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