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[11C]Flumazenil brain uptake is influenced by the blood-brain barrier efflux transporter P-glycoprotein.
Leiden University.
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2012 (English)In: EJNMMI research, ISSN 2191-219X, Vol. 2, 12- p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: [11C]Flumazenil and positron emission tomography (PET) are used clinically to assess gamma-aminobutyric acid (GABA)-ergic function and to localize epileptic foci prior to resective surgery. Enhanced P-glycoprotein (P-gp) activity has been reported in epilepsy and this may confound interpretation of clinical scans if [11C]flumazenil is a P-gp substrate. The purpose of this study was to investigate whether [11C]flumazenil is a P-gp substrate.

METHODS: [11C]Flumazenil PET scans were performed in wild type (WT) (n = 9) and Mdr1a/1b, (the genes that encode for P-gp) double knockout (dKO) (n = 10) mice, and in naive rats (n = 10). In parallel to PET scanning, [11C]flumazenil plasma concentrations were measured in rats. For 6 of the WT and 6 of the dKO mice a second, [11C]flumazenil scan was acquired after administration of the P-gp inhibitor tariquidar. Cerebral [11C]flumazenil concentrations in WT and Mdr1a/1b dKO mice were compared (genetic disruption model). Furthermore, pre and post P-gp-blocking cerebral [11C]flumazenil concentrations were compared in all animals (pharmacological inhibition model).

RESULTS: Mdr1a/1b dKO mice had approximately 70% higher [11C]flumazenil uptake in the brain than WT mice. After administration of tariquidar, cerebral [11C]flumazenil uptake in WT mice increased by about 80% in WT mice, while it remained the same in Mdr1a/1b dKO mice. In rats, cerebral [11C]flumazenil uptake increased by about 60% after tariquidar administration. Tariquidar had only a small effect on plasma clearance of flumazenil.

CONCLUSIONS: The present study showed that [11C]flumazenil is a P-gp substrate in rodents. Consequently, altered cerebral [11C]flumazenil uptake, as observed in epilepsy, may not reflect solely GABAA receptor density changes but also changes in P-gp activity.

Place, publisher, year, edition, pages
2012. Vol. 2, 12- p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-185288DOI: 10.1186/2191-219X-2-12PubMedID: 22455873OAI: oai:DiVA.org:uu-185288DiVA: diva2:571162
Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2013-08-13

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Syvänen, StinaEriksson, Jonas

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