[3H]Para-amino-clonidine: A novel ligand which binds with high affinity to α-adrenergic receptors

Bruno R. Rouot, Solomon H. Snyder

Research output: Contribution to journalArticlepeer-review


Para-amino-clonidine (PAC) is an α-adrenergic agonist with extraordinarily high potency in some peripheral tissues. We have demonstrated the labeling of α-adrenergic binding sites in central and peripheral tissues with [3H]PAC and compared properties of this binding to those of [3H]clonidine. [3H]PAC binds saturably with a dissociation constant (KD) of about 0.9 nM to rat cerebral cortex membranes. It has about 2-3 times the affinity of [3H]clonidine for α-receptor binding sites. The greater affinity is attributable mainly to a slower dissociation of [3H]PAC than [3H]clonidine from binding sites. The relative and absolute potencies of various adrenergic agonists and antagonists in competing for [3H]PAC and [3H]clonidine binding are essentially the same. [3H]PAC can also be utilized to label α-adrenergic binding sites in the kidney and spleen where the relative potencies of PAC and clonidine are the same as in the brain.

Original languageEnglish (US)
Pages (from-to)769-774
Number of pages6
JournalLife Sciences
Issue number9
StatePublished - Aug 27 1979

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)


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