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アルツハイマー病、他の認知症、老化 1
Alzheimer's Disease, Other Dementia, Aging 1

開催日 2014/9/11
時間 14:00 - 15:00
会場 Room I(311+312)
Chairperson(s) 植木 孝俊 / Takatoshi Ueki (名古屋市立大学大学院医学研究科機能解剖学分野 / Department of Functional Anatomy, Nagoya City University Graduate School of Medical Sciences, Japan)
髙橋 淳 / Jun C. Takahashi (国立循環器病研究センター 脳神経外科 / Department of Neurosurgery, National Cerebral and Cardiovascular Center, Japan)

Differences in the densities of α4β2 and α7 nicotinic acetylcholine receptors in the living human brain

  • O1-I-3-2
  • 尾内 康臣 / Yasuomi Ouchi:1 寺田 達弘 / Tatsuhiro Terada:1 中泉 享子 / Kyoko Nakaizumi:2 吉川 悦次 / Etsuji Yoshikawa:3 垣本 晃宏 / Akihiro Kakimoto:3 磯部 卓志 / Takashi Isobe:3 鈴木 いおり / Iori Suzuki:3 植木 孝俊 / Takatoshi Ueki:4 間賀田 泰寛 / Yasuhiro Magata:5 
  • 1:浜松医科大学・MPRC・生体機能イメージング / Dept Biofunct Imaging, Med Photon Res Ctr, Hamamatsu Univ Sch Med, Japan 2:浜松医大・医・精神 / Dept Psychiat, Hamamatsu Univ Sch Med, Japan 3:浜松ホトニクス / Hamamatsu Photonics KK, Japan 4:浜松医大・医・解剖(神経機能) / Dept Neuroanat, Hamamatsu Univ Sch Med, Japan 5:浜松医科大学・MPRC・分子病態イメージング / Dept Mol Imaging, Med Photon Res Ctr, Hamamatsu Univ Sch Med, Japan 

It is considered that α4β2 nicotinic acetylcholine receptors (nAChRs) in the brain modulate brain functions related to emotion, attention and memory, whereas α7 nAChRs are associated with learning and memory functions. Since we have already reported in vivo pattern of α4β2 nAChRs binding in the human brain, here we report in vivo distribution of α7 nAChRs using positron emission tomography (PET) with [11C]Me-QAA, a new tracer for α7 nAChRs and discuss the difference in their binding.
Nine cognitively normal subjects and additional 4 Alzheimer's disease (AD) patients participated in the α7 nAChRs PET study. All subjects were evaluated with neuropsychological tests and conventional MRIs. As reported in our previous α4β2 nAChRs ([18F]2FA) PET study with 25 healthy participants, we first examined whether a simplified evaluation method could replace the dynamic full scan protocol by comparing a SRTM-estimated binding potential (BPND) with a ratio index (RI) calculated simply by dividing target PET counts by the reference counts on the delayed tracer accumulation images. We then compared the distribution of the two tracers binding.
Unlike a good positive correlation between [18F]2FA BPND and [18F]2FA RI in any brain regions, such a correlation failed to be found in the [11C]Me-QAA PET study, and high or low binding sites were more difficult to be detected when using [11C]Me-QAA RI. This was remarkable when it came to the comparison in the disease state. There was a marked difference in the distribution of the binding of these two nAChRs tracers.
The present results suggest that [11C]Me-QAA may have a non-negligible amount of non-specific binding character, so that a model-based analysis such as SRTM is necessary to evaluate its binding in vivo. In contrast to the [18F]2FA binding, [11C]Me-QAA binds more to the cortical regions. This indicates that the α7 nAChRs are present more extensively than the α4β2 nAchRs in the human brain.

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