The Relationship Between Nicotinic Receptors and Cognitive Functioning in Healthy Aging: An In Vivo Positron Emission Tomography (PET) Study With 2-[18F]Fluoro-A-85380

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ABSTRACTExtensive experimental and neuropathological evidence supports the general hypothesis that decline in the basal forebrain cholinergic system contributes significantly to age-related cognitive impairment. Postmortem studies suggest reductions in neuronal nicotinic acetylcholine receptors (nAChRs, particularly the α4β2 subtype) with aging. This study aimed to determine the distribution of α4β2-subtype nAChRs in vivo by 2-FA PET in healthy subjects (aged 21-83) and to establish whether there is an age-related decline in nAChRs. Furthermore, the relationship between PET measures of 2-FA binding and neurobehavioral measures of cognitive function was investigated. All participants were nonsmokers and underwent extensive cognitive testing and a PET scan after injection of 2-FA (200 MBq). Brain regional 2-FA binding was assessed through a simplified estimation of distribution volume (DVS). As expected, increasing age was associated with poorer cognitive performance, particularly on tasks assessing episodic memory and attentional processes. No significant age-related differences in regional nAChR DVS were found. Furthermore, no significant correlations were found between cognitive measures and nAChR DVS. These results are consistent with recent studies suggesting the stability of cholinergic markers during senescence. It is plausible that changes in α4β2 nAChRs do occur with advancing age, but are beyond detection by the clinical 2-FA PET approach adopted here. However, this approach may be appropriate for use in pathologies considered to undergo extensive nAChR loss such as Alzheimer's disease and Parkinson's disease.

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