title: Differential effects of age on human striatal adenosine A₁ and A(2A) receptors.
abstract: The aim of this study was to investigate the effect of age on the distribution of adenosine A₁ receptors (A₁Rs) and adenosine A(2A) receptors (A(2A)Rs) in the striatum of healthy subjects using PET imaging with 8-dicyclopropylmethyl-1-[¹¹C]methyl-3-propylxanthine ([¹¹C]MPDX) and [7-methyl-¹¹C]-(E)-8-(3,4,5-trimethoxystyryl)-1,3,7-trimethylxanthine ([¹¹C]TMSX), respectively. We recruited 8 young (22.0 ± 1.7 years) and 10 elderly (65.4 ± 7.6 years) volunteers to undergo [¹¹C]MPDX PET scanning, and 11 young (22.7 ± 2.7 years) and six elderly (60.7 ± 8.5 years) volunteers to undergo [¹¹C]TMSX PET scanning. A dynamic series of decay-corrected PET scans was performed for 60 min following injection of [¹¹C]MPDX or [¹¹C]TMSX. We calculated the binding potential (BP(ND) ) of [¹¹C]MPDX and distribution volume ratio (DVR) of [¹¹C]TMSX in the striatum. The BP(ND) of [¹¹C]MPDX was significantly lower in elderly than in young subjects, both in the putamen and head of the caudate nucleus. The BP(ND) was negatively correlated with age in both the putamen and the head of the caudate nucleus. However, no difference was found between the DVR of [¹¹C]TMSX in the striata of young and elderly subjects, nor was there a correlation between age and the DVR of [¹¹C]TMSX. The effect of age on the distribution of A₁Rs in the human striatum described herein is similar to previous reports of age-related decreases in dopamine D₁ and D₂ receptors. Unlike A₁Rs, however, this study suggests that the distribution of A(2A) Rs does not change with age.
authors.affiliation: The Second Department of Internal Medicine, Nippon Medical School, Bunkyo-Ku, Tokyo, Japan; Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, Itabashi-Ku, Tokyo, Japan. mishina@nms.ac.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Mishina
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kimura
authors.forename: Mika
authors.initials: M
authors.lastname: Naganawa
authors.forename: Kenji
authors.initials: K
authors.lastname: Ishii
authors.forename: Keiichi
authors.initials: K
authors.lastname: Oda
authors.forename: Muneyuki
authors.initials: M
authors.lastname: Sakata
authors.forename: Jun
authors.initials: J
authors.lastname: Toyohara
authors.forename: Shiro
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Katayama
authors.forename: Kiichi
authors.initials: K
authors.lastname: Ishiwata
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D003342:Corpus Striatum / Q000737:chemistry* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D043682:Receptor, Adenosine A1 / Q000032:analysis*; D043705:Receptor, Adenosine A2A / Q000032:analysis*; D014970:Xanthines
chemical_list: C451639:1-methyl-8-dicyclopropylmethyl-1-methyl-3-propylxanthine; C405422:KF18446; D043682:Receptor, Adenosine A1; D043705:Receptor, Adenosine A2A; D014970:Xanthines