Assessment of neuroreceptor changes in healthy ageing and in Alzheimer’s disease with emission tomography Gitte M. Knudsen * Neurobiology Research Unit 9201, Rigshospitalet, 9 Blegdamvej, DK-2100 Copenhagen O, Denmark Received 21 November 2002; accepted 31 January 2003 Abstract In healthy subjects, a number of different receptor systems show a moderate decline with age whereas in Alzheimer’s disease (AD) several of these receptor system show marked reductions. On the basis of postmortem studies, decreases in particular 5-HT 2 receptors, nicotinic a4-h2, and a preferential loss of M2 as compared to M1 muscarinic receptors have been found. Some of these findings have been partially replicated in in vivo imaging studies but the heterogeneity of the patients, the small sample sizes, and the problems with shortcomings in the radiotracer characteristics are all factors that have been limiting for appropriate interpretations. Molecular imaging methods hold a very high potential as powerful tools for demonstrating more basic pathophysiological processes. It is anticipated that with the rapid development of better, quantifiable, and specific tracers, also including probes for detection of gene expression, molecular imaging will be able to contribute substantially to bridge between, at one hand, the enormous progress seen at the molecular level with that of the clinical entity of AD. It will also continue to provide an efficient tool for diagnosing and monitoring disease progress and treatment efficacy. D 2003 Elsevier Science B.V. All rights reserved. Keywords: Molecular imaging; PET; SPECT; Ageing; Alzheimer’s disease 0531-5131/03 D 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0531-5131(03)00100-6 * Tel.: +45-3545-6720; fax: +45-3545-6713. E-mail address: gitte@nru.dk (G.M. Knudsen). International Congress Series 1252 (2003) 299 – 308