μ Opiate receptors are selectively labelled by [3H]carfentanil in human and rat brain

Milt Titeler, Robert A. Lyon, Michael J. Kuhar, James F. Frost, Robert F Dannals, Sigrun Leonhardt, Amy Bullock, Laura T. Rydelek, Donald L. Price, Robert G. Struble

Research output: Contribution to journalArticle

Abstract

[11C]Carfentanil is a potent opioid agonist currently in use as a specific PET (position emission tomography) scan radioligand for brain μ opioid receptors. In order to investigate the receptor interactions of carfentanil in detail [3H]carfentanil was used as a radioligand for labelling receptors in rat and human brain tissue homogenates. [3H]Carfentanil was found to bind saturably and with high affinity (KD = 0.08 ± 0.01 nM) to membranes prepared from human cortical (Bmax = 42 ± 3 fmol/mg) and thalamic (Bmax = 84 ± 3 fmol/mg) tissues and rat cortex (Bmax = 82 ± 4 fmol/mg) and deincephalon (Bmax = 105 ± 5 fmol/mg). Association (1.23 ± 0.19 × 1010Mol-1 × min-1 and dissociation rate (0.19 ± 0.03 min-1) constants were determined in human cortical tissues; results from studies in rat cortical, and rat diencephalon tissue homogenates produced similar kinetic rate constants. Competition studies with a variety of drugs indicated that [3H]carfentanil interacts primarily with μ opioid receptors in the four tissues studied; the affinities of a series of non-radioactive opioid ligands were essentially identical in the four tissues (correlation coefficients = 0.88-0.93). Naloxone, morphine, DAGO ([D-Ala2-MePhe4-Gly-ol5]enkephalin), DADL (D-Ala2-D- Leu5]enkaphalin) and EKC (ethylketazocine) potently displaced specific [3H]carfentanil binding with nM potency while the κ agonist U-69593, the σ agonists (+)-SKF 10047, (+)-3-PPP ((3-hydroxyphenyl)-N-propylpiperidine) and haloperidol and PCP (phencyclidine) were less potent displacing agents. The higher affinities of DAGO and morphine versus DADL for the [3H]carfentanil binding site indicates that δ opioid receptors are not being labelled. These data indicate that [3H]carfentanil is a high affinity, specific μ opioid receptor radioligand that may be of use in vitro for studying μ opioid receptors and supports the PET scanning data indicating the μ opioid receptor specificity of [11C]carfentanil. The molecular kinetic rate constants determined in vitro will be of assistance in using modelling procedures to interpret PET scanning information.

Original languageEnglish (US)
Pages (from-to)221-228
Number of pages8
JournalEuropean Journal of Pharmacology
Volume167
Issue number2
DOIs
StatePublished - Aug 22 1989

Fingerprint

carfentanil
Opioid Receptors
Brain
Tomography
Morphine
Opioid Analgesics
Ethylketocyclazocine
Phencyclidine
Diencephalon
Enkephalins
Haloperidol

Keywords

  • PET scanning
  • [H]Carfentanil
  • μ Opioid receptors

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Pharmacology

Cite this

μ Opiate receptors are selectively labelled by [3H]carfentanil in human and rat brain. / Titeler, Milt; Lyon, Robert A.; Kuhar, Michael J.; Frost, James F.; Dannals, Robert F; Leonhardt, Sigrun; Bullock, Amy; Rydelek, Laura T.; Price, Donald L.; Struble, Robert G.

In: European Journal of Pharmacology, Vol. 167, No. 2, 22.08.1989, p. 221-228.

Research output: Contribution to journalArticle

Titeler, M, Lyon, RA, Kuhar, MJ, Frost, JF, Dannals, RF, Leonhardt, S, Bullock, A, Rydelek, LT, Price, DL & Struble, RG 1989, 'μ Opiate receptors are selectively labelled by [3H]carfentanil in human and rat brain', European Journal of Pharmacology, vol. 167, no. 2, pp. 221-228. https://doi.org/10.1016/0014-2999(89)90582-7
Titeler, Milt ; Lyon, Robert A. ; Kuhar, Michael J. ; Frost, James F. ; Dannals, Robert F ; Leonhardt, Sigrun ; Bullock, Amy ; Rydelek, Laura T. ; Price, Donald L. ; Struble, Robert G. / μ Opiate receptors are selectively labelled by [3H]carfentanil in human and rat brain. In: European Journal of Pharmacology. 1989 ; Vol. 167, No. 2. pp. 221-228.
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