Use of 3-quinuclidinyl 4-iodobenzilate as a receptor binding radiotracer

3-Quinuclidinyl 4-iodobenzilate was shown to bind to the muscarinic acetylcholine receptor (mAChR) by testing the saturability and the stereoselectivity in the corpus striatum, cerebellum, and the heart. But the ratio of radioactivity in tissues containing different concentrations of mAChR was less than the ratio of mAChR concentrations determined by in vitro saturation assay. As a result, the sensitivity to change in receptor concentration by external imaging will be reduced for this receptor binding radiotracer.