In addition to the dysfunction and neuronal loss in basal forebrain regions, confirmation of cholinergic losses comes from studies that report deterioration in the activity of acetylcholine esterase (AChE) and choline acetyltransferase (ChAT), reduced acetylcholine (ACh) release, and decreased level of nicotinic and muscarinic receptors in the AD affected brain [23]. Here, CHAT is linked to Alzheimer disease.