Cited by 256Cannabis and Cannabinoid ResearchRadiopharmaceutical Chemistry and ApplicationsNeuropeptides and Animal Physiology

123I-labeled AM251: a radioiodinated ligand which binds in vivo to mouse brain cannabinoid CB1 receptors

Gatley, S.John, Gifford, Andrew N., Volkow, Nora D., Lan, Ruoxi, Makriyannis, Alexandros·1996·European Journal of Pharmacology

Abstract

We have investigated the binding of 123I-labeled N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methy l-1 H-pyrazole-3-carboxamide (AM251), an analog of the cannabinoid receptor antagonist SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-me thyl-1 H-pyrazole-3-carboxamide] in the mouse brain. Following intravenous injection, the peak whole-brain uptake of about 1% of the administered activity occurred at about 2 h. By 8 h radioactivity in brain had declined to about half its peak value. High-performance liquid chromatographic analysis showed that > 70% of radioactivity extracted from brain at 2 h was still present as [123I]AM251. Co-injection of SR141716A inhibited the in vivo brain binding of [123I]AM251 dose dependently. At 2 mg/kg, the highest dose that could be tested, inhibition was 50% at 2 h post-administration. The ED50 value calculated assuming that 2 mg/kg gave near-maximal inhibition was about 0.1 mg/kg. In contrast to the brain, radioactivity in other major organs (blood, liver, kidney, heart and lung) was little affected by SR141716A. The regional binding of [123I]AM251 in the brain was consistent with the published distribution of cannabinoid receptors in rat brain, in that the order was hippocampus, striatum > cerebellum > brain stem. delta 9-Tetrahydrocannabinol co-administered intravenously at 10 mg/kg, a dose which induced catalepsy and decreased locomotor activity, decreased the 2 h brain uptake of [123I]AM251 by 10%, but this was not significant (P = 0.08). In in vitro binding assays with mouse hippocampal membranes, tetrahydrocannabinol inhibited binding of [123I]AM251 with an IC50 value of about 700 nM, compared with about 0.2 nM for SR141716A.

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Crossref · 10.1016/0014-2999(96)00279-8

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  • Increased [11C]OMAR VT values are explained to the most part by receptor up-regulation in response to low anandamide levels rather than low receptor occupancy by anandamide.

    “The lack of displacement of CB1 radioligands by agonists42–44 which has been attributed to a large receptor reserve45 suggests that increased [11C]OMAR VT values are explained to the most part by receptor up-regulation in response to low anandamide levels rather than low receptor occupancy by anandamide.”

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Authors
Gatley, S. J., Gifford, A. N., Volkow, N. D., Lan, R., & Makriyannis, A.
Affiliations
  • Brookhaven National Laboratory (US)
  • University of Connecticut (US)
Corresponding author
Gatley, S.John
Venue
European Journal of Pharmacology
Publisher
Elsevier BV
Published
1996-07
Volume
307
Issue
3
Pages
331-338
ISSN
0014-2999 (ISSN-L)
OpenAlex
W1979829009
Cited by
252
References
15
Citations by year
2026: 2 · 2025: 3 · 2024: 2 · 2023: 3 · 2022: 1 · 2021: 4 · 2020: 3 · 2019: 2 · 2018: 7 · 2017: 1 · 2016: 8 · 2015: 12 · 2014: 8 · 2013: 13 · 2012: 11
FWCI
1.49
Type
journal article
Language
en
Open access
closed
Locations
  • European Journal of Pharmacology (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • U.S. Department of Energy
  • Sanofi
  • National Institute on Drug Abuse (DA-06278, R01DA006278, DA07515, DA-03801)
  • Brookhaven National Laboratory
Topics
  • Health Sciences › Medicine › Pharmacology › Cannabis and Cannabinoid Research
  • Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Radiopharmaceutical Chemistry and Applications
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuropeptides and Animal Physiology
Keywords
CB1 receptor, radioiodination, SR141716A, radioligand binding, brain receptor distribution, tetrahydrocannabinol, delta-9-tetrahydrocannabinol, hippocampus, striatum, cerebellum, brainstem
MeSH terms
Rimonabant, Animals, Brain, Cell Membrane, Chromatography, High Pressure Liquid, Hippocampus, Iodine Radioisotopes, Isotope Labeling, Male, Mice, Inbred Strains, Motor Activity, Piperidines, Protein Binding, Pyrazoles, Radioligand Assay, Receptors, Drug, Dronabinol, Tissue Distribution, Receptors, Cannabinoid, Mice

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