CHRNA4 and Alzheimer disease: In a study of the cholinergic system during AD progression through measurement of mRNA expression levels in nucleus basalis neurons, Mufson et al. found no changes of mAChR subtypes M1–M5, nAChR subunits α1–6, and β1–4 in patients with AD or MCI compared to the group with no cognitive impairment (NCI).