In vitro and ex vivo distribution of [3H]harmane, an endogenous β-carboline, in rat brain

Neil J. Anderson, Robin J. Tyacke, Stephen M. Husbands, David J. Nutt, Alan L. Hudson, Emma S.J. Robinson

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42 Citations (SciVal)


The endogenous β-carboline, harmane, has been shown to bind to monoamine oxidase A (MAO-A) and a separate, high affinity, non-MAO site. Research in our laboratory has shown that harmane is an active component of clonidine-displacing substance (CDS), the proposed endogenous ligand for imidazoline binding sites (IBS). In the present study we have investigated the distribution of [3H]harmane in rat brain, and related the binding profile to the distribution of the MAO-A selective ligand [3H]Ro41- 1049 and the I2BS ligand [3H]2-BFI. The in vivo distribution of [3H]harmane following intravenous administration was also investigated. Receptor autoradiography revealed a highly significant correlation for the distribution of [3H]harmane and [ 3H]Ro41-1049, and a significant correlation for [3H] harmane and the I2BS ligand [3H]2-BFI. The in vivo distribution of [3H]harmane suggests that the ligand accumulates in the adrenal gland and throughout the brain with the primary route of excretion occurring via the duodenum. In conclusion, these studies have shown that [ 3H]harmane labels a population of binding sites that reflect the distribution of MAO-A. Further evidence for a non-MAO, IBS [3H] harmane population has not been shown but the high level of expression of the MAO-A site is likely to have masked the much smaller population of I 2BS.

Original languageEnglish
Pages (from-to)269-276
Number of pages8
Issue number3
Publication statusPublished - Mar 2006

Bibliographical note

Funding Information:
The Medical Research Council, UK, The Wellcome Trust, UK and Philippe Delagrange, IRIS, France for providing funding for this research.


  • Brain
  • Harmane
  • Imidazoline binding site
  • Monoamine oxidase A
  • Pharmacokinetics
  • Receptor autoradiography

ASJC Scopus subject areas

  • Pharmacology
  • Cellular and Molecular Neuroscience


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