Abstract
The present work demonstrates quantitative autoradiography by using positron emission tomography tracers and storage phosphorimaging plates. The uptake and association of [11C]N-methyl-4-piperidylbenzilate was measured in rat brain tissue cryosections of various thicknesses. The signal increased with increasing section thickness, but only in 10-μm-thick sections did the binding reach the steady state during a 50-min observation time. This violation of the equilibrium condition, potentially combined with perfusion limitations, leads to erroneous increased binding-site density and decreased affinity in the 25- and 50-μm-thick sections. For better imaging of receptor distribution it is reasonable to use thicker sections. For quantitative analysis of receptor-binding parameters, the specific properties of ligands at different thicknesses of cryosections need to be considered. Evidence is provided that the nonselective muscarinic antagonistN-methyl-4-piperidylbenzilate binds preferentially to the M4 subtype of muscarinic acetylcholine receptors.
Footnotes
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Send reprint requests to: Mats Bergström, UAS, Uppsala University PET Centre, S-75185 Uppsala, Sweden. E-mail:mats.bergstrom{at}pet.uu.se
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↵1 This work is planned to be used in Sven Sihver’s Ph.D. thesis.
- Abbreviations:
- PET
- positron emission tomography
- [11C]NMPB
- 11C-labeledN-methyl-4-piperidylbenzilate
- ROI
- region of interest
- M1 to M5
- acetylcholine muscarinic receptor subtypes
- Received January 15, 1999.
- Accepted March 22, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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