title: Acute effects of L-tryptophan on brain extracellular 5-HT and 5-HIAA levels in chronic experimental portal-systemic encephalopathy.
abstract: Portal-systemic encephalopathy (PSE) is associated with increased brain turnover of serotonin (5-hydroxytryptamine; 5-HT). Despite this metabolic increase, neuronal release of 5-HT is unaltered in neocortex of portacaval shunted (PCS) rats. In the present study, frontal neocortical extracellular 5-HT and 5-hydroxyindole-3-acetic acid (5-HIAA) levels were determined in PCS rats and sham-operated controls prior to, as well as, after acute challenge with L-tryptophan (L-TRP; a bolus dose of 280 mg/kg i.p. followed by 5 consecutive hourly doses of 50 mg/kg). Neither basal 5-HT nor 5-HIAA extracellular levels were significantly altered in PCS rats compared to controls. L-TRP administration resulted in unaltered extracellular 5-HT but elevated 5-HIAA levels in PCS and sham rats. These findings do not suggest that changes in brain neuronal 5-HT release play any major functional role in the pathogenesis of chronic PSE. The present data also emphasize the importance of distinguishing between brain 5-HT metabolism and brain 5-HT release.
authors.affiliation: Department of Clinical Pharmacology, Lund University, Sweden.
authors.forename: P B
authors.initials: PB
authors.lastname: Bergqvist
authors.forename: S
authors.initials: S
authors.lastname: Hjorth
authors.forename: G
authors.initials: G
authors.lastname: Apelqvist
authors.forename: F
authors.initials: F
authors.lastname: Bengtsson
mesh_terms: D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D002908:Chronic Disease; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism*; D006501:Hepatic Encephalopathy / Q000378:metabolism*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D011167:Portacaval Shunt, Surgical; D011168:Portal System / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000494:pharmacology*
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan