Effect of aging on cerebral A1 adenosine receptors: A [18F]CPFPX PET study in humans

Cerebral A1 adenosine receptors (A1AR) fulfill important neuromodulatory and homeostatic functions. The present study examines possible age-related A1AR changes in living humans by positron emission tomography (PET) and the A1AR ligand [18F]CPFPX. Thirty-six healthy volunteers aged 22–74 years were included. The apparent binding potential (BP′2BP′2) of [18F]CPFPX in various cerebral regions was calculated non-invasively using the cerebellum as reference region. In addition, the total distribution volume (DV′tDV′t) was assessed in 10 subjects undergoing arterial blood sampling. There was no significant association between regional DV′tDV′t and age, gender, caffeine consumption or sleep duration. BP′2BP′2 showed a significant age-dependent decrease in all regions except cingulate gyrus (p = 0.062). The BP′2BP′2 decline ranged from −17% (striatum) to −34% (postcentral gyrus), the average cortical decline being −23%. There was no significant effect of gender, caffeine consumption and sleep duration on BP′2BP′2. In line with in vitro animal studies, the present in vivo PET study detected an age-dependent A1AR loss in humans that may be of pathophysiological importance in various neurological diseases associated with aging. Because of the discrepant results of the invasive (DV′tDV′t) and the non-invasive (BP′2BP′2) analyses the present study needs further validation.