Binding of benzodiazepines and some major metabolites at their sites in normal human frontal cortex in vitro

E. Richelson, A. Nelson, R. Neeper

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

Using [3H]flunitrazepam in radioligand binding assays, we determined equilibrium dissociation constants (K(d)'s) at 37°C for 22 benzodiazepines (15 parent compounds and 7 major metabolites) at benzodiazepine binding sites in human frontal cortex. This list included several compounds never studied before at human receptors. Although dissociation was too rapid to measure reliably at this temperature, the K(d)'s for flunitrazepam were not significantly different when either rapid filtration or centrifugation was used to separate the bound from free radioligand. The most potent compound was triazolam (K(d) = 0.54 nM); the least potent, chlordiazepoxide (K(d) = 0.54 nM); the least potent, chlordiazepoxide (K(d) = 684 nM). The K(d)'s were significantly lower (about 3- to 7-fold) for several compounds tested at an equilibrium temperature of 0°C compared to those obtained at 37°C. There was a strong correlation for 15 compounds for the log K(d) at rat brain receptors (data obtained from the literature) vs. the log K(d) for human brain. In addition, the log K(d)'s of the various benzodiazepines for their receptor were significantly correlated with the log of their minimum daily dosages used to treat patients. Many of the benzodiazepines have clinically important active metabolites that have higher affinity for benzodiazepine binding sites in human brain than their parent compounds. Such data have important implications in the clinical use of these compounds.

Original languageEnglish (US)
Pages (from-to)897-901
Number of pages5
JournalJournal of Pharmacology and Experimental Therapeutics
Volume256
Issue number3
StatePublished - 1991

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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