@article{oai:repo.qst.go.jp:00046043,
 author = {Kodaka, Fumitoshi and Ito, Hiroshi and Takano, Harumasa and Takahashi, Hidehiko and Arakawa, Ryosuke and Miyoshi, Michie and Okumura, Masaki and Otsuka, Tatsui and Nakayama, Kazuhiko and Halldin, Christer and Farde, Lars and Suhara, Tetsuya and 小高 文聰 and 伊藤 浩 and 高野 晴成 and 高橋 英彦 and 荒川 亮介 and 三好 美智恵 and 奥村 正紀 and 大塚 達以 and ハルディン クリスタ and 須原 哲也},
 issue = {1},
 journal = {The International Journal of Neuropsychopharmacology},
 month = {Feb},
 note = {The increased proportion of the high-affinity state of dopamine D2/3 receptors (D2,high) is assumed to correlate with dopamine hypersensitivity, implying a relationship with psychotic symptoms observed in psychiatric disorders such as schizophrenia. [11C](R)-2-CH3O-N-n-propylnorapomorphine ([11C]MNPA), which has an agonistic property to dopamine D2 receptors (D2Rs), is expected to bind preferentially to D2,high. The occupancy of dopamine D2Rs by antagonists to receptors has not been investigated using [11C]MNPA. We compared dopamine D2R occupancies by risperidone, an antagonist to receptors, between [11C]MNPA and [11C]raclopride to confirm whether risperidone occupies D2,high and D2,low at almost identical proportions. PET studies were performed on 11 healthy men under resting condition and following oral administration of a single dose of risperidone (0.5-2.0 mg). Striatal receptor occupancy for each radioligand was calculated. The relationship between dose or plasma concentration of risperidone and dopamine D2R occupancy was calculated. Striatal dopamine D2R occupancies measured with [11C]MNPA and [11C]raclopride were 22-65% and 24-69%, respectively. In the striatum, ED50 values measured with [11C]MNPA and [11C]raclopride were 0.98 and 1.03 mg, respectively. The striatal ED50 values as calculated from plasma concentration were 9.15 ng/ml and 8.01 ng/ml, respectively. Almost identical occupancies and ED50 values were observed between the two radioligands, indicating that risperidone bound to D2,high and D2,low at almost identical proportions in a dose-dependent manner.},
 pages = {83--89},
 title = {Effect of Risperidone on High-Affinity State of Dopamine D2 Receptors:a PET Study with Agonist Ligand [11C](R)-2-CH3O-N-n-propylnorapomorphine},
 volume = {14},
 year = {2011}
}