Quantification of neuroreceptors in living human brain. V. Endogenous neurotransmitter inhibition of haloperidol binding in psychosis

Albert Gjedde, Dean F. Wong

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

The half-inhibition concentration (IC50) of a drug indicates its ability to inhibit the binding of other ligands of a receptor. The authors used positron emission tomography to test the hypothesis that haloperidol's IC50 toward the binding of tracer N-[11C]methylspiperone ([11C]NMSP) in brain must be increased in patients in whom more dopamine is bound to receptors than in healthy volunteers. The IC50 of haloperidol was significantly elevated from 1.5 nmol/L in healthy volunteers and patients with bipolar disease without psychosis to 4.5 nmol/L in patients with schizophrenia or bipolar disease with psychosis. The higher IC50 values in psychosis are consistent with an 8-fold increased binding of dopamine and a 16-fold elevated concentration of synaptic dopamine in psychosis. At the 80% haloperidol blockade of the receptors, the calculated amount of neurotransmitter bound in the patients with psychosis declined to twice the value estimated in the nonpsychotic subjects, that is, 5 pmol cm-3.

Original languageEnglish
Pages (from-to)982-994
Number of pages13
JournalJournal of Cerebral Blood Flow and Metabolism
Volume21
Issue number8
DOIs
StatePublished - 2001
Externally publishedYes

Keywords

  • Dopamine
  • Neuroleptics
  • Neuroreceptors
  • Positron emission tomography

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