Augmented brain 5-HT crosses the blood-brain barrier through the 5-HT transporter in rat.
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.
Nakatani
Yasushi
Y
Department of Physiology, Toho University School of Medicine, 5-21-16, Omori-nishi, Ota-ku, Tokyo 143-8540, Japan.
Sato-Suzuki
Ikuko
I
Tsujino
Naohisa
N
Nakasato
Akane
A
Seki
Yoshinari
Y
Fumoto
Masaki
M
Arita
Hideho
H
D006916:5-Hydroxytryptophan / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D008297:Male; D017551:Microdialysis; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins / Q000187:drug effects / Q000378:metabolism*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology
D006916:5-Hydroxytryptophan; D012701:Serotonin; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors