CHAT and Alzheimer disease: For example, in one AD animal model, the intracerebroventricular administration of the cholinotoxic ethylcholine aziridinium (AF64A) resulted in reduced choline acetyltransferase (ChAT) activity and increased acetylcholinesterase (AChE) in the hippocampus of 4- and 12-month-old rats, but no effects were observed in 22-month-old rats, which indicated age-dependent effects on AF64A-mediated cholinotoxicity (El Tamer et al., 1996).