Muscarinic acetylcholine receptors in Alzheimer's disease. In vivo imaging with iodine 123-labeled 3-quinuclidinyl-4-iodobenzilate and emission tomography.

In vivo imaging of muscarinic acetylcholine receptor binding function in a patient with Alzheimer's disease, using single-photon emission computed tomography and iodine 123-labeled 3-quinuclidinyl-4-iodobenzilate (123I-QNB), and perfusion imaging using 123I-N-isopropyl p-iodoamphetamine are described. A profound decrease in perfusion to the posterior temporal and parietal cortex and a more uniform uptake of 123I-QNB throughout the cerebral cortex were observed. The 123I-QNB activity ratio was reduced compared with that of a normal age-matched subject, suggesting a moderate impairment in muscarinic receptor binding function in Alzheimer's disease. Furthermore, and more importantly, our study demonstrates that images of in vivo receptor binding can be obtained easily and nontraumatically using 123I-QNB and single-photon emission computed tomography.