Document Detail

Human brainstem serotonin receptors: characterization and implications for subcortical myoclonus.
MedLine Citation:
PMID:  8937789     Owner:  NLM     Status:  MEDLINE    
The immediate serotonin (5-HT) precursor, 5-hydroxy-L-tryptophan (L-5-HTP), is an investigational treatment for myoclonic disorders. Its mechanism of action in humans is incompletely understood. We measured the density of subtypes of 5-HT1 and 5-HT2 receptors and the affinity of 5-HT and L-5-HTP in vitro in the human brainstem and cortex, regions associated with subcortical and cortical myoclonus, respectively. In the cortex, the rank order of 5-HT receptor subtype Bmax was 5-HT2A (low-affinity), 5-HT1A, 5-HT uptake sites, 5-HT1D, 5-HT2C, 5-HT1E/F, and 5-HT2A (high-affinity) sites. In the brainstem, the rank order was 5-HT uptake sites, 5-HT1D, 5-HT2C, 5-HT1A, and 5-HT2A(L) sites. Specific binding at 5-HT1E/F and high-affinity 5-HT2A sites was too low for characterization. In competition studies, 5-HT had high affinity for 5-HT1A and 5-HT2C sites in the brainstem and cortex, but L-5-HTP was > 1,000-fold less active. These data support the hypothesis that in humans L-5-HTP stimulates 5-HT receptors in the CNS only after conversion to 5-HT. They also indicate in the human brainstem a prominence of 5-HT1A sites and paucity of 5-HT1D, 5-HT1E/F, and 5-HT2A sites, which has implications for brainstem-mediated myoclonus and response to serotonergic drugs.
M R Pranzatelli; I Galvan; P T Tailor
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Clinical neuropharmacology     Volume:  19     ISSN:  0362-5664     ISO Abbreviation:  Clin Neuropharmacol     Publication Date:  1996 Dec 
Date Detail:
Created Date:  1997-03-05     Completed Date:  1997-03-05     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  7607910     Medline TA:  Clin Neuropharmacol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  507-14     Citation Subset:  IM    
Department of Neurology, George Washington University, Washington, D.C., USA.
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MeSH Terms
5-Hydroxytryptophan / metabolism
Binding, Competitive
Brain Stem / metabolism,  ultrastructure*
Cerebral Cortex / metabolism,  ultrastructure
Middle Aged
Myoclonus / metabolism*
Receptors, Serotonin / classification*,  metabolism*
Serotonin / metabolism
Grant Support
FD-U-000746/FD/FDA HHS
Reg. No./Substance:
0/Receptors, Serotonin; 50-67-9/Serotonin; 56-69-9/5-Hydroxytryptophan

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