Nicotinic acetylcholine receptor imaging for dementia

Recently, a number of evidences have been found that dysfunctions of cholinergic nerve systems play a substantial role in various types of dementia. Cholinesterase inhibitors were revealed to improve the cognitive symptoms of vascular dementia and dementia with Leby bodies (DLB) as well as those of Alzheimer's disease (AD). Postmortem studies showed the reduction of nicotinic acetylcholine receptors (nAChRs) in AD, DLB and Parkinson's disease (PD), especially α4β2 subtype. Recently, 5-iodo-3-(2(S)-azetidinylmethoxy) pyridine (5IA) has been synthesized as a radioligand for imaging nAChR with SPECT. It shows high affinity toward α4β2 subtype and good safety. We investigated 5IA SPECT in patients with AD and PD. The reductions of nAChR were shown in almost all brain regions of both diseases, which is consistent with autoradiographic studies. Therefore, 5IA SPECT may become a useful tool for a wide range of dementia.